System, method and apparatus evaluating tissue temperature

ABSTRACT

Method, system and apparatus for monitoring target tissue temperatures wherein temperature sensors are configured as passive resonant circuits each, with a unique resonating signature at monitoring temperatures extending below a select temperature setpoint. The resonant circuits are configured with an inductor component formed of windings about a ferrite core having a Curie temperature characteristic corresponding with a desired temperature setpoint. By selecting inductor winding turns and capacitance values, unique resonant center frequencies are detectable. Temperature monitoring can be carried out with implants at lower threshold and upper limit temperature responses. Additionally, the lower threshold sensors may be combined with auto-regulated heater implants having Curie transitions at upper temperature limits.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/466,223, filed Apr. 28, 2003 and is acontinuation-in-part of U.S. application Ser. No. 10/246,347, filed Sep.18, 2002 which is a continuation of U.S. patent application Ser. No.10/201,363 filed Jul. 23, 2002, claiming the benefit of U.S. ProvisionalApplication No. 60/349,593 filed Jan. 18, 2002.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] A beneficial response elicited by a heating of neoplastic tissuewas reported by investigators in 1971. See the following publications inthis regard:

[0004] (1) Muckle, et al., “The Selective Inhibitory Effect ofHyperthermia on the Metabolism and Growth of Malignant Cells” Brit J. ofCancer 25:771-778 (1971).

[0005] (2) Castagna, et al., “Studies on the Inhibition by Ethionine ofAminoazo Dye Carcinogenesis in Rat Liver.” Cancer Research 32:1960-1965(1972).

[0006] While deemed beneficial, applications of such thermotherapyinitially were constrained to external surface heating. When externalapplications have been employed the resultant body structure heating hasbeen described as having been uncontrolled in thermal localizationresulting in temperature elevation of the whole body. Employment ofdiathermy has been reported with a resultant non-destructive inhibitoryreaction. In general, no consensus by investigators as to the efficacyof thermotherapy with respect to tumor was present as late as the mid1970s. See generally:

[0007] (3) Strom, et al., “The Biochemical Mechanism of Selective HeatSensitivity of Cancer Cells—IV. Inhibition of RNA Synthesis.” Europ. J.Cancer 9:103-112 (1973).

[0008] (4) Ziet. fur Naturforschung 8, 6: 359.

[0009] (5) R. A. Holman, Letter “Hyperthermia and Cancer”, Lancet, pp.1027-1029 (May 3, 1975).

[0010] Notwithstanding a straightforward need for more effectivetechniques in the confinement of thermotherapy to localized internallylocated target tissue regions, investigators have established that tumorcells may be physiologically inhibited by elevating their temperaturesabove normal body temperature, for example, 37° C. for one majorpopulation, to a range exceeding about 40° C. The compromising butbeneficial results further are predicated upon that quantum of thermalexposure achieved, based upon the time interval of controlled heatapplication. Thus, effective thermotherapies are characterized by anapplied quantum of thermal energy established within a restrictivetissue periphery or volume of application with an accurately controlledtemperature over an effective component of time.

[0011] One modality of thermotherapy is termed “hyperthermia” therapy,an approach to thermal treatment at temperatures elevated withinsomewhat narrow confines above normal body temperature. For instance,the elevation above a normal body temperature of 37° C. typically willfall within a range of 42° C. to 45° C. While higher temperaturetherapies have been described, hyperthermia therapy conventionally looksto affecting tissue to the beneficial effect of, for instance, negatingneoplastic development, while avoiding denaturization, i.e., cell deathor necrosis. It follows that an embracing of this therapeutic modalitycalls for the application of thermal control over specific tissuevolumes.

[0012] Confinement of thermotherapy to a neoplasm-suspect target tissuevolume internally disposed within the body without a generation ofdamage to healthy surrounding tissue has been considered problematic andthus the subject of diverse investigation. Experience in this field hasrevealed that achieving a controlled, thermo-therapeutic level of heatthroughout a targeted tissue volume is difficult. In general, thedistribution of induced heat across such tissue volumes can exhibitsubstantial variations. Vascularity and densities of heterogeneoustissues may impose such variations. For instance, the cooling propertiesof blood flow complicate the maintenance of a desired thermal dose atthe target volume. A variety of approaches toward intra-body localizedheat applications have evolved. Such efforts generally have been basedupon the application of microwave energy (U.S. Pat. No. 4,138,998); theapplication of acoustic wave-based systems (ultrasound); the applicationof electric fields at RF frequencies (direct RF) from transmittingantenna arrays including an application subset utilizing inductivesystems driven at relatively lower frequencies within the RF realm, andthe utilization of infra red heaters.

[0013] Ultrasound is considered to be an acoustic wave above the normalrange of human hearing, i.e., above about 20,000 Hertz. When employedclinically for thermo-therapeutic as well as diagnostic purposes,ultrasound system configurations perform in recognition of the acousticimpedance of investigated tissue. Acoustic impedance is the resistanceto wave propagation through tissue, for example, due to absorbance,reflectance or molecularly induced scattering. Accordingly, the subjecttissue volume will absorb some of the energy from the ultrasound wavespropagated through it and the kinetic energy associated with the energyabsorbed is converted into thermal energy to thus raise tissuetemperature. See generally U.S. Pat. No. 6,451,044. When implementingultrasound thermotherapy systems, careful control is called for toassure that minimum threshold tissue temperatures are reached and thatmaximum tissue temperature limits are not exceeded. Heretofore,temperature monitoring generally has been carried out by percutaneouslyinjecting or otherwise inserting tethered temperature sensors such asthermocouples or thermistors into the targeted tissue region. Insertionof a tethered thermocouple may be accomplished by first inserting ahypodermic needle, then inserting a catheter through the needle with thesensor at its tip, whereupon the needle is withdrawn. Where hyperthermiatherapy or heat induced immunotherapy are carried out, maintenance ofrelatively narrow temperature targets is sought, calling for a highlevel of control. For these thermotherapies, typically multiple therapysessions are required, thus the generally undesirable injection orinsertion of temperature sensors must be carried out for each of whatmay be many treatment sessions.

[0014] One approach has been advanced for ultrasound-basedthermotherapy. In that approach, thermal localization is achieved bydeveloping constructive wave interference with phased array-based waveguide applicators mounted to extend around the patient (see U.S. Pat.Nos. 5,251,645 and 4,798,215).

[0015] The microwave band generally is considered to extend from about900 Mhz. Clinical studies have established that thermotherapy systemscan be implemented with microwave radiating devices. Early endeavorsutilizing microwave-based hyperthermia treatment evidenced difficultiesin heating target tissue volumes at adequate depth while preventingsurrounding superficial healthy tissue from incurring pain or damage dueto hot spots exhibiting temperatures greater than about 44-45° C.However, later developments using adaptive phased array technology hasindicated that relatively deeply located target tissues can be heated tothermotherapeutic temperatures without inducing the earlierdifficulties. See generally the following publication:

[0016] (6) Fenn, et al, “An Adaptive Microwave Phased Array For TargetedHeating Of Deep Tumors In Intact Breast: Animal Studies Results” Int. J.Hyperthermia, Vol. 15, No. 1, pp 45-61 (1999).

[0017] Inductively-based approaches to thermotherapy systems havereceived important attention by investigators. The coil transmittedoutputs of these systems generally are focused for field convergencetoward the target tissue volume and the resultant, internally thermallyaffected tissue region has been monitored in situ by thermo-responsivesensors such as rod-mounted thermocouples and thermistors. Thosetethered heat sensors are inserted percutaneously into the target tissueregion, being coupled by extra-body electrical leads extending toconnections with temperature monitoring readouts. As before, theinvasiveness of the monitoring electrical leads extending into thepatients' body for this procedure has been considered undesirable. Thisparticularly holds where repetitive but time-spaced procedures arecalled for, or the therapeutic modality is employed in thermallytreating tumor within the brain.

[0018] The radio (RF) spectrum is defined as extending from the audiorange to about 300,000 MHz. However direct RF thermotherapy has beendescribed in conjunction with the 80 MHz to 110 MHz range.

[0019] Another approach is described as performing as a focused radiofrequency/microwave region system, the election between these spectralregions being determined with respect to the depth of the target tissue.See: htp://www.bsdme.com/.

[0020] Efforts to regionalize or confine therapeutic tissue heating topredefined borders or volumetric peripheries have included procedureswherein small wire or iron-containing crystals (U.S. Pat. No. 4,323,056)are implanted strategically within the tissue region of interest.Implantation is achieved with an adapted syringe instrumentality.Electromagnetic fields then are introduced to the region to inductivelyheat the implanted radiative-responsive heater components and thus evokea more regionally controlled form of thermotherapy. In one suchapproach, ferromagnetic thermoseeds have been employed which exhibitCurie temperature values somewhat falling within the desired temperaturerange for an elected thermotherapy. This achieves a form of selfregulation by operation of the system about those Curie transitions. Forinstance, as radiative inductive excitation drives the thermoseeds totemperatures to within the permeability based state change levelsassociated with attainment of a Curie temperature range, the thermoseedsbecome immune to further application of external excitation energy. (Seegenerally U.S. Pat. No. 5,429,583). Unfortunately, the Curie transitiontemperature range of the thermoseeds is relatively broad with respect tothe desired or target temperature. This expanded Curie transition rangeis, in part, the result of the presence of the ferrite-based seedswithin relatively strong electromagnetic fields. The result is asomewhat broad and poor regulation temperature band which may amount 10°or more. As a consequence, the auto-regulated devices are constrained touses inducing tissue necrosis or ablation, as opposed to uses withtemperatures controlled for hyperthermia therapies.

[0021] See generally:

[0022] (7) Brezovich, et al., “Practical Aspects of FerromagneticThermoseed Hyperthermia.” Radiologic Clinics of North America, 27:589-682 (1989).

[0023] (8) Haider, et al., “Power Absorption in Ferromagnetic Implantsfrom Radio Frequency Magnetic Fields and the Problem of Optimization.”IEEE Transactions On Microwave Theory And Techniques, 39: 1817-1827(1991).

[0024] (9) Matsuki et al., “An Optimum Design Of A Soft Heating SystemFor Local Hyperthermia” IEEE Transactions On Magnetics, 23(5):2440-2442, (September 1987).

[0025] Thermotherapeutic approaches designed to avoid the subcutaneousinsertion of one or more temperature sensors have looked to the controlof heating using modeling methodology. These approximating modelingmethods are subject to substantial error due to differences or vagariesexhibited by the heterogeneous tissue of any given patient. Suchdifferences may be due to variations in vascularity, as well as thegradual metamorphosis of a tumor mass. The latter aspect may involvesomewhat pronounced variations in tissue physiologic characteristicssuch as density. See generally the following publication:

[0026] (10) Ackin, H. et al., “Recent Development In Modeling HeatTransfer in Blood Perfused Tissue.” IEEE Transactions on Bio-MedicalEngineering, 41 (2): 97-107 (1994).

[0027] Some aspects of thermotherapy have been employed as an adjunct tothe use of chemotherapeutic agents in the treatment of tumor. Because ofthe precarious blood supply or vascularity and of the high interstitialfluid presence, such agents may not be effectively delivered to achievea 100% cell necrosis. Further the tumor vessel wall may pose a barrierto such agents, and resultant non-specific delivery may lead tosignificant systemic toxicities. Studies have addressed these aspects ofchemotherapy, for instance, by the utilization of liposomes toencapsulate the chemotherapeutic agents to achieve preferential deliveryto the tumor. However the efficiencies of such delivery approaches havebeen somewhat modest. Clinically, hyperthermia therapy has been employedas a form of adjunct therapy to improve the efficiency of moreconventional modalities such as radiation therapy and chemotherapy. Forthe latter applications the thermal aspect has been used to augmentbloodstream borne release agents or liposome introduction to the tumorsite. Hyperthermia approaches have been shown to trigger agent releasefrom certain liposomes, making it possible to release liposome contentsat a heated site (U.S. Pat. Nos. 5,490,840; 5,810,888). For any suchthermotherapeutic application, an accurate temperature control at thesitus of the release is mandated. See the following publications:

[0028] (11) Kong, et al., “Efficacy of Lipsomes and Hyperthermia in aHuman Tumor Xenograft Model: Importance of Triggered Drug Release.”Cancer Research, 60: 6950-6957 (2000).

[0029] (12) Chung, J. E., et al., “Thermo-Responsive Drug Delivery FromPolymeric Micelles Using Block Co-Polymers of Poly(N-isopropylacrylamide-b-butylmethacrylate) and Poly(butylmethacrylate), Journal of Controlled Release (Netherlands), 62(2):115-127 (Nov. 1, 1999).

[0030] Hyperthermia when used in conjunction with radiation treatment ofmalignant disease has been demonstrated as beneficial for destroying aspecific tumor site. Clinical data has evolved demonstrating an improvedefficacy associated with combined radiation and hyperthermia treatmentsas compared to radiation therapy alone. Such multimodal therapy conceptsalso have been extended to a combination of hyperthermia treatment withboth radiation treatment and chemotherapy (radiochemotherapy). Seegenerally:

[0031] (13) Falk et al., “Hyperthermia In Oncology” Int. J.Hyperthermia, 17: 1-18 (2001).

[0032] Biological mechanisms at the levels of single cells activated byheat became the subject of scientific interest in the early 1960s asconsequence of the apparently inadvertent temperature elevation of anincubator containing Drosophila melanogaster (fruit flies). Thesecreatures, upon being heat shocked, showed the characteristic puffsindicative of transcriptional activity and discrete loci. See thefollowing publication:

[0033] (14) Ritossa, “A New Puffing Pattern Induced By Temperature Shockand DNP in Drosophila.” Experientia, 18: 571-573(1962).

[0034] These heat shock loci encoding the heat shock proteins (HSPs),became models for the study of transcriptional regulation, stressresponse and evolution. The expression of HSPs may not only be inducedby heat shock, but also by other mechanisms such as glucose deprivationand stress. Early recognized attributes of heat shock proteins residedin their reaction to physiologically support or reinvigorate heatdamaged tissue. (See U.S. Pat. No. 5,197,940). Perforce, this wouldappear to militate against the basic function of thermotherapy when usedto carry out the denaturization of neoplastic tissue. However, heatshock phenomena exhibit a beneficial attribute where the thermal aspectsof their application can be adequately controlled. In this regard,evidence that HSPs, possess unique properties that permit their use ingenerating specific immune responses against cancers and infectiousagents has been uncovered. Additionally, such properties have beensubjects of investigation with respect to boney tissue repair,transplants and other therapies. See generally the followingpublications:

[0035] (15) Anderson et al., “Heat, Heat Shock, Heat Shock Protein andDeath: A Central Link in Innate and Adoptive Immune Responses.”Immunology Letters, 74: 35-39 (2000).

[0036] (16) Srivastava, et al, “Heat Shock Proteins Come of Age:Primitive Functions Acquire New Role In an Adaptive World.” Immunity,8(6): 657-665 (1998).

[0037] Beneficial thermal compromization of target tissue volumes is notentirely associated with HSP based treatments for neoplastic tissue andother applications, for instance, having been studied in connection withcertain aspects of angioplasty. Catheter-based angioplasty was firstintentionally employed in 1964 for providing a transluminal dilation ofa stenosis of an adductor hiatus with vascular disease. Balloonangioplasty of peripheral arteries followed with cautious approaches toits implementation to the dilation of stenoatic segments of coronaryarteries. By 1977 the first successful percutaneous transluminalcoronary angioplasty (PTCA) was carried out. While, at the time,representing a highly promising approach to the treatment of anginapectoris, subsequent experience uncovered post-procedural complications.While PTCA had been observed to be effective in 90% or more of thesubject procedures, acute reclosure, was observed to occur inapproximately 5% of the patients. Stenosis was observed to occur in somepatients within a period of a few weeks of the dilational procedure andrestenosis was observed to occur in 15% to 43% of cases within sixmonths of angioplasty. See generally:

[0038] (17) Kaplan, et al., “Healing After Arterial Dilatation withRadiofrequency Thermal and Non-Thermal Balloon Angioplasty Systems.”Journal of Investigative Surgery, 6: 33-52 (1993).

[0039] In general, the remedy for immediate luminal collapse has been aresort to urgent or emergency coronary bypass graft surgery. Thus, theoriginal procedural benefits attributed to PTCA were offset by the needto provide contemporaneous standby operating room facilities andsurgical personnel. A variety of modalities have been introduced toavoid post PTCA collapse, including heated balloon-based therapy,(Kaplan, et al., supra) the most predominate being the placement of astent extending intra-luminally across the dilational situs. Such stentscurrently are used in approximately 80% to 90% of all interventionalcardiology procedures. While effective to maintain or stabilizeintra-luminal dilation against the need for emergency bypass procedures,the stents are subject to the subsequent development of in-stentstenosis or restenosis (ISR). See generally:

[0040] (18) Holmes, Jr., “In-Stent Restenosis.” Reviews inCardiovascular Medicine, 2: 115-119 (2001).

[0041] Debulking of the stenotic buildup has been evaluated using lasertechnology; rotational atherectomy; directional coronary atherectomy;dualistic stent interaction (U.S. Pat. No. 6,165,209); repeated balloonimplemented dilation, the application of catheter introduced heat to thestent region (U.S. Pat. No. 6,319,251); the catheter-borne delivery ofsoft x-rays to the treated segment, sonotherapy; light activation; localarterial wall alcohol injection; and ultrasound heating of a stentformed of an ultrasound absorptive material (U.S. Pat. No. 6,451,044).

[0042] See additionally the following publications with respect toatherectomy for therapeutically confronting restenosis:

[0043] (19) Bowerman, et al., “Disruption of Coronary Stent DuringArtherectomy for Restenosis.” Catherization and CardiovascularDiagnosis, 24: 248-251 (1991).

[0044] (20) Meyer, et al., “Stent Wire Cutting During CoronaryDirectional Atherectomy.” Clin. Cardiol,. 16: 450-452 (1993).

[0045] In each such approach, additional percutaneous intervention iscalled for. See generally the following publication:

[0046] (21) Vliestra and Holmes, Jr., Percutaneous Transluminal CoronaryAngioplasty Philadelphia: F. A. Davis Co. (Mayo Foundation) (1987).

[0047] Other approaches have been proposed including the application ofelectrical lead introduced electrical or RF applied energy to metallicstents, (U.S. Pat. No. 5,078,736); the incorporation of radioisotopeswith the stents (U.S. Pat. Nos. 6,187,037; 6,192,095); and resort todrug releasing stents (U.S. Pat. No. 6,206,916 B1). While non-invasivecontrol of ISR has been the subject of continued study, the developmentof a necessarily precise non-invasively derived control over it hasremained an elusive goal.

[0048] Another application of hyperthermia is in orthopedics, as a meansto stimulate bone growth and fracture healing. There are several FDAapproved devices for stimulation of bone growth or healing, each withlimitations and side effects. Therapies include invasive electricalstimulation, electromagnetic fields, and ultrasound stimulation. Decadesold research has claimed a stimulation of bone growth by a mild increasein temperature of the boney tissue. Previous researchers have used suchmethods as inductive heating of implanted metal plates, or heating coilswrapped around the bone. The utility of these methods is limited by theinvasive nature of the surgery needed to implant the heating elementsand the inability to closely control tissue temperature. Moreover,therapeutic benefits have been inconsistent between different studiesand experimental protocols. For a summary of past work, see generally:

[0049] (22) Wootton, R. Jennings, P., King-Underwood, C., and Wood, S.J., “The Effect of Intermittent local Heating on Fracture Healing in theDistal Tibia of the Rabbit.” International Orthopedics, 14: 189-193(1990).

[0050] A number of protocols have demonstrated a beneficial effect ofhyperthermia on bone healing. Several studies indicate temperatureaffects bone growth and remodeling after injury. Hyperthermia may bothimprove blood supply and stimulate bone metabolism and have a directeffect on bone-forming cells by inducing heat shock proteins or othercellular proteins. In one experiment, rabbit femurs were injured bydrilling and insertion of a catheter. Hyperthermia treatments were givenat four-day intervals for 2-3 weeks using focused microwave radiation.Bones which had suffered an insult as a result of the experimentalprocedure showed a greater density of osteocytes and increased bone masswhen treated with hyperthermia. Injured bones treated with hyperthermiashowed completely ossified calluses after two weeks, while theseprocesses normally take four weeks in untreated injuries. One problemwith microwave heating of bone mass is the difficulty in predicting heatdistribution patterns and maintaining the target tissue within theappropriate heat range.

[0051] When tissue is heated at too high of temperature, there can beirreversible cytotoxic effects which could damage bone and othertissues, including osteogenic cells, rather than induce healing. Certainstudies have shown that induction of mild heat shock promotes bonegrowth, while more severe heat shock inhibits bone growth. Therefore,control and monitoring of the temperature of the targeted bone tissue isimperative to achieve therapeutic benefit and avoid tissue damage.

[0052] See additionally the following publications with respect tohyperthermia for therapeutically promoting osteogenesis:

[0053] (23) Leon, et al., “Effects of Hyperthermia on Bone. II. Heatingof Bone in vivo and Stimulation of Bone Growth.” Int. J. Hyperthermia 9:77-87 (1993).

[0054] (24) Shui et al., “Mild heat Shock Induces Proliferation,Alkaline Phosphatase Activity, and Mineralization in Human Bone MarrowStromal Cells and Mg-63 Cells In Vitro.” Journal of Bone and MineralResearch 16: 731-741 (2001).

[0055] (25) Huang, C.-C., Chang, W. H., and Liu, H.-C. “Study on theMechanism of Enhancing Callus Formation of Fracture by UltrasonicStimulation and Microwave Hyperthermia.” Biomed. Eng. Appl. Basis Comm.10: 14-17 (1998).

[0056] Existing protocols for therapeutically promoting osteogenesis arelimited by the invasive nature and concomitant potential for infectionfor instance with tethered electrical stimulators; poor temperaturecontrol, and potential for tissue injury or reduced therapeutic benefit,for instance with microwave heating or other induced electromagneticfields; difficulty in effectively applying therapy to the injured bonebecause of targeting difficulties or low patient compliance withprescribed repetitive therapy.

[0057] The host immune system can be activated against infectiousdisease by heat shock protein chaperoned peptides in a manner similar tothe effect seen against metastatic tumors. Heat shock proteinschaperoning peptides derived from both viral and bacterial pathogenshave been shown to be effective at creating immunity against theinfectious agent. For infectious agents for which efficacious vaccinesare not currently available (especially for intracellular pathogens e.g.viruses, Mycobacterium tuberculosis or Plasmodium) HSP chaperonedpeptides may be useful for the development of novel vaccines. It isexpected that purified HSP chaperoned peptides (e.g. gp96 complexes)used as vaccines for diseases caused by highly polymorphic infectiousagents would be less effective against genetically distinct pathogenpopulations. For a summary of past work on HSP vaccines againstinfectious agents, see generally:

[0058] (26) Neiland, Thomas J. F., M. C. Agnes A. Tan, MoniqueMonnee-van Muijen, Frits Koning, Ada M. Kruisbeek, and Grada M. vanBleek, “Isolation of an immunodonminant viral peptide that isendogenously bound to stress protein gp96/GRP94.” Proc. Nat'l Acad. Sci.USA, 93: 6135-6139 (1996).

[0059] (27) Heikema, A., Agsteribbe, E., Wilschut, J., Huckriede, A.,“Generation of heat shock protein-based vaccines by intracellularloading of gp96 with antigenic peptides.” Immunology Letters, 57: 69-74(1997).

[0060] (28) Zugel, U., Sponaas, A. M., Neckermann, J., Schoel, B., andKaufmann, S. H. E., “gp96-Peptide Vaccination of Mice AgainstIntracellular Bacteria.” Infection and Immunity, 69: 4164-4167 (2001).

[0061] (29) Zugel, U., and Kaufmann, S. H. E., “Role of Heat ShockProteins in Protection from and Pathogenesis of Infectious Diseases.”Clinical Microbiology Reviews, 12: 19-39 (1999).

[0062] In commonly owned co-pending application for U.S. Pat. Ser. No.10/246,347, filed Sep. 18, 2002 and entitled “System, Method andApparatus for Localized Heating of Tissue”, an approach to accuratelycarrying out an in situ elevation of the temperature of a target tissuevolume is presented. Accuracy is achieved using unteathered temperaturesensor implants formed of ferromagnetic material which experiences anabrupt magnetic permeability state change within a very narrowtemperature range. Temperature sensing is carried out by monitoring avery low level magnetic field extending through the position of theimplant. For instance, the earth's magnetic field may be employed. Whereinductively based heating is utilized, non-magnetic heaters may beimplanted with the sensors and sensing is carried out intermittently inthe absence of the inductably derived magnetic field.

BRIEF SUMMARY OF THE INVENTION

[0063] The present invention is addressed to method, system andapparatus for accurately evaluating a temperature related physicalparameter within the body of a patient. Accurate temperature measurementis achieved through the use of one or more teatherless temperaturesensors strategically located within the body and configured with apassive resonant circuit. These passive circuits respond to an extrabody applied excitation electromagnetic field by resonating at anidentifiable unique resonant center frequency. In one embodiment, theresonant circuit based sensors are configured with a capacitor and aseries coupled inductor formed with a winding disposed about a ferritecore. That ferrite core is formulated to exhibit a somewhat sharppermeability state change or transition at a Curie temperaturecorresponding with a desired temperature setpoint. With the arrangement,upon being excited by an applied excitation burst, the sensor will ringor resonate at its unique, signature resonant center frequency when atmonitor temperatures below the involved Curie temperature. As the sensorwitnesses monitoring temperatures approaching the Curie temperaturedefined setpoint the intensity of its unique resonant center frequencydecreases, an aspect which may be taken advantage of from a temperaturecontrol standpoint. However, when the Curie or target temperature isreached, the relative permeability of the sensor's ferrite core dropssharply toward a unity value to, in turn, cause a sharp drop in thereluctance of the associated inductor coil causing the resonantfrequency of the device to shift substantially upward in value. Thisshift is to an off-scale value. In effect, the signature outputdisappears. As the sensors resonate in response to excitation, thedetector components of the associated interrogation system are capableof sensing all of the resonating devices, whereupon the sensed signalsare digitized, averaged and analyzed to identify each sensor by itsunique resonant center frequency, if at the noted monitor temperatures.Such analysis may be carried out using a Fourier transform-typeapproach. Because the unique resonant center frequency remains stable asthe temperatures witnessed by the sensors, approach or transition towardthe Curie temperature-based setpoint, the amplitude of the Fouriertransform signal will diminish and the system has the capability ofpredicting the arrival of the Curie based setpoint temperature. Thermalovershoot can thus be more accurately accommodated for.

[0064] The unique resonant center frequencies of the sensors are readilyestablished by adjusting the value of inductance and/or capacitance ofthe passive resonant circuits. In general, the unique resonant centerfrequencies are developed within a frequency band ranging from about 100kHz to about 2 MHz. Accordingly, a substantial range of sensorsignatures are available to the system.

[0065] A feature of the system and method of the invention is concernedwith a typical patient management regimen wherein a relativelysubstantial repetition of thermotherapeutic procedures is called for.The sensors remain in position with respect to the target tissue volumeand may, in this regard, be fashioned with anchors for the purpose ofmigration avoidance. Where a succession of treatments is involved, notonly is there no requirement to re-install sensors, but also, thealignment of excitation and sensing antennae as well as heating unitoutput orientations essentially are simply repeated. Another aspect ofthis feature resides in the utilization of the pre-implanted sensors asa conventional tumor situs marker for subsequent patient evaluationimaging procedures.

[0066] In one embodiment of the invention one or more of the sensorimplants are configured to exhibit Curie transitions at a lowerthreshold setpoint temperature, while an additional one or more areconfigured to exhibit Curie transitions at an upper limit highersetpoint temperature. Thus, the practitioner will be apprised of thetarget tissue volume reaching that minimum temperature adequately fortherapy, as well as of any temperature excursions above the upper limit.Where such thermal excursions occur, the heating unit involved may beadjusted, for example, in terms of power level as well as componentpositioning.

[0067] Those sensor implants configured to identify attainment of alower threshold temperature setpoint may be combined with ferrite coreimplemented auto-regulating heater implants having Curie transitions atan upper limit higher temperature setpoint. This particular combinationwill be beneficial where the thermotherapy temperature levels involvedwill approach apoptosis or necrosis levels, as well as for thepreviously mentioned hyperthermia therapy administered in the rangebetween approximately 40° C. and 45° C.

[0068] The instant method has brought application to thermotherapyendeavors including an in vivo induction of heat shock proteins, aprocedure having important utility in the treatment of cancer,infectious diseases and other therapies. As another modality, one ormore of the sensors is combined with an intra-luminal stent and when socombined and implanted, permit a non-invasive repeatable and accuratehyperthermia therapy for stenosis/restenosis.

[0069] The implant control heating approach of the invention also may beapplied to the field of orthopedics. In this regard, the sensorcomponents may be combined in intimate thermal exchange relationshipwith non-magnetic metal bone support devices implanted with bony tissue.The setpoint temperature elected for such modality is selected toenhance the repair of the mending bony tissue.

[0070] Implant based controlled in vivo heating according to theprecepts of the invention also may be employed as a vehicle for inducingimmunity against or for the treatment of diseases cause by infectiousagents.

[0071] Other objects of the invention will, in part, be obvious andwill, in part appear hereinafter.

[0072] The invention, accordingly, comprises the method, system andapparatus possessing the construction, combination of elements,arrangement of parts and steps which are exemplified in the followingdetailed description.

[0073] For a fuller understanding of the nature and objects of theinvention, reference should be made to the following detaileddescription taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0074]FIG. 1 is a partial schematic view of a prior art approach toheating a target tissue volume utilizing an auto-regulating heaterimplant;

[0075]FIG. 2 shows curves relating relative permeability withtemperature for sensors employing ferromagnetic components;

[0076]FIG. 3 is a generalized semi-log curve illustrating the temporalrelationship between the duration of application of a given temperatureto tissue with the value of critical temperatures;

[0077]FIG. 4 illustrates a prior art approach to heating a targetedtissue volume utilizing tethered heat sensors located within the targettissue volume;

[0078]FIG. 5 shows curves relating relative permeability under low levelapplied magnetic field intensities and under high level applied magneticfield intensities;

[0079]FIG. 6 is a flowchart illustrating the production of ferrites;

[0080]FIG. 7 is an electrical schematic diagram of a passive resonantcircuit configured to provide temperature sensing;

[0081]FIG. 8 is a schematic block diagram of a temperature monitoringsystem according to the invention;

[0082]FIG. 9 is an oscillotrace showing a sensing response andassociated resonant frequency intensity;

[0083]FIG. 10A is a representation of the FFT relative amplitudes offour sensors at temperatures below a setpoint temperature;

[0084]FIG. 10B is a representation of the FFT relative amplitudes of thesensors of FIG. 10A during a Curie transition;

[0085]FIG. 10C is a set of curves relating the relative amplitudes oftwo sensors positioned with temperature sensors within a water bathenvironment;

[0086] FIGS. 11A-11F are electrical schematic diagrams showing anexcitation circuit employed with the system of the invention;

[0087] FIGS. 12A-12D are electrical schematic diagrams showing adetector circuit employed with the system of the invention;

[0088]FIG. 13 illustrates a block diagram of the interrogation system ofthe invention;

[0089]FIG. 14 is a perspective view of a sensor according to theinvention;

[0090]FIG. 14A is a sectional view of the sensor shown in FIG. 14 takenthrough the plane 14A-14A shown in FIG. 14B;

[0091]FIG. 14B is an end view of the sensor of FIG. 14A;

[0092]FIG. 14C is a top view of the sensor of FIG. 14A with componentsshown in phantom;

[0093]FIG. 15 is a perspective view of an auto-regulating heaterimplant;

[0094]FIG. 15A is a sectional view of the auto-regulating implant shownin FIG. 15;

[0095]FIG. 15B is an end view of the implant of FIG. 15A;

[0096]FIG. 15C is a perspective view of an implant according to theinvention which incorporates an anchor;

[0097]FIG. 158D is a sectional view of the auto-regulating heater ofFIG. 15C;

[0098]FIG. 16 is a schematic and sectional view of an implant locatinginstrument which may be used with the implants of the invention showingthe instrument prior to releasing the implant in a targeted tissuevolume'

[0099]FIG. 17 is a schematic sectional view of the instrument of FIG. 16showing the delivery of a sensor implant into a targeted tissue volume;

[0100]FIG. 18 is a schematic view of a target tissue volume with a mapform of location of temperature sensing implants;

[0101]FIG. 19 is a schematic representation of one embodiment of thesystem of the invention;

[0102]FIG. 20 is a graph schematically showing tissue temperatureresponse to controlled extra body heating according to the invention;

[0103] FIGS. 21A-21G combine as labeled thereon to provide a flowchartillustrating a procedure and control carried out with the system of FIG.19;

[0104]FIG. 22 is a chart illustrating an intermittent heating andinterrogating feature of the system of the invention, the chart beingbroken along its timeline in the interest of clarity;

[0105] FIGS. 23A-23H combine as labeled thereon to provide a flowchartillustrating another intermittent procedure and control carried out withthe system represented in FIG. 19;

[0106] FIGS. 24A-24G combine as labeled thereon to provide a flowchartillustrating an intermittent procedure and control employing bothsensors and auto-regulating heaters as carried out with the systemrepresented in FIG. 19;

[0107]FIG. 25 is a schematic representation of another embodiment of thesystem of the invention;

[0108] FIGS. 26A-26J combine as labeled thereon to provide a flowchartillustrating the procedures and control carried out with the systemrepresented in FIG. 25;

[0109]FIG. 27 is a schematic sectional representation of a combinedstent and temperature sensor according to the invention embedded withina blood vessel;

[0110]FIG. 28 is a sectional view taken through the plan 28-28 in FIG.27;

[0111]FIG. 29 is a sectional schematic view of a stent according to theinvention incorporating a heat activated release agent coating and beingshown embedded within a blood vessel;

[0112]FIG. 30 is a sectional view taken through the plane 30-30 in FIG.29;

[0113]FIG. 31 is a schematic sectional view of another stent embodimentaccording to the invention, the device being shown embedded within ablood vessel;

[0114]FIG. 32 is a sectional view taken through the plane 32-32 shown inFIG. 31;

[0115]FIG. 33 is a sectional schematic view of a stent embedded within ablood vessel and having been retrofitted with a sensor assemblyaccording to the invention;

[0116]FIG. 34 is a sectional view taken through the plane 34-34 shown inFIG. 33;

[0117]FIG. 35 is a sectional schematic view of a stent embedded within ablood vessel and showing a retrofit thereof with two sensor assembliesaccording to the invention;

[0118]FIG. 37 is a schematic representation of another embodiment of thesystem of the invention;

[0119] FIGS. 38A-38B combine as labeled thereon to illustrate an initialstent implantation procedure;

[0120] FIGS. 39A-39H combine as labeled thereon to provide a flowchartillustrating the procedure and control carried out within the systemrepresented in FIG. 37;

[0121]FIG. 40 is an electrical schematic diagram of another sensoraccording to the invention employing a passive resonant circuit withtemperature responsive capacitance;

[0122]FIG. 41 is a graph plotting capacitance variation with a desiredtemperature range; and

[0123]FIG. 42 is a graph schematically showing the graph of FIG. 40 incombination with an inductor core component exhibiting substantiallyuniform relative permeability over a temperature range of interest.

DETAILED DESCRIPTION OF THE INVENTION

[0124] While a variety of techniques for evolving an effectiveinterstitial thermotherapy of target tissue volumes have been approachedby investigators, an earlier development deemed somewhat promisinginvolved the implantation of ferromagnetic alloy heaters sometimesreferred to as “ferromagnetic seeds” within that volume. Theferromagnetic alloy heaters were adapted so as to alter in exhibitedmagnetic permeability in consequence of temperature. For example, withthis arrangement, when a Curie temperature transition range wasthermally reached, permeability would, in turn, diminish over thetransition range and correspondingly thermal responsiveness to anapplied inductive field would diminish. Thus it was opined that atemperature auto-regulation could be achieved to optimize a thermallybased implantation therapy. Such an arrangement is depicted in FIG. 1.Here, the treatment modality is represented generally at 10 wherein atarget tissue volume, for example, comprised of neoplastic tissue, isshown symbolically within dashed region 12 located internally within thebody of patient 14. Within the target tissue volume 12 a ferromagneticmaterial (e.g., ferromagnetic alloy comprising primarily palladium andcobalt) auto-regulating heater implant 16 is embedded which is, forinstance, inductively heated from the excited inductive coil 18 of analternating current field (ACF) heating assembly 20. The ferromagneticimplants as at 16 exhibit a temperature-related relative magneticpermeability, μ_(r). Such relative permeability may be represented bycurve 22 shown in FIG. 2. Relative permeability is expressed as μ_(r)=μ/μ_(o), where μ=absolute permeability (Henry/meter), μ_(o)=aconstant=magnetic permeability of free space (Henry/meter) and μ_(r) istherefore dimensionless but ranges from a value of unity to 100,000 ormore. Curve 22 reveals that the relative magnetic permeability, μ_(r),decreases as the temperature of the ferromagnetic alloy heaterapproaches its Curie temperature, T_(c). Since the induced electricfield heating power in an object is proportional to the square root ofmagnetic permeability, a decrease in magnetic permeability withelevation of temperature is associated with a corresponding decrease inthe heating power associated with inductive heating.

[0125] Traditionally, the change in magnetic permeability offerromagnetic alloys with increasing temperature has not been abrupt aswould be preferred for precise temperature regulation of an implantedheating component as at 16. In this regard, characteristic curve 22reveals that under the relatively intense, applied fields a permeabilitytransition occurs gradually over a span typically of 10° C. to 15° C. ormore. Responses of ferromagnetic-based auto-regulators as represented atcurve 22 are occasioned both by the formulation of the ferromagneticmaterial as well as its reaction to the imposed inductive field which issomewhat unavoidable for auto-regulation. As a result, the implantedheater device 16 may not reach the intended Curie temperature andresultant relative permeability of unity. Often, that elevation intemperature above normal body temperature has not been achieved.Accordingly, accommodation has been made by electing Curie temperaturetransition ranges falling well above what would have otherwise been atarget temperature for thermotherapy with a result that criticaltemperature limits of the tissue being treated have been exceeded.Because of such performance, thermotherapy utilizing suchauto-regulating heating implants has been constrained to developinghigher temperatures including those deriving necrosis or cell death.Thermotherapeutic procedures also are prone to inaccuracies by virtue ofthe unknown environmental conditions within which an implant as at 16 issituated. With respect to such unknown phenomena, temperatures achievedwith ferromagnetic implants will vary depending upon cooling phenomenawithin the tissue surrounding the device. Such phenomena occur, forexample, as a consequence of the degree of vascularity in the targetregion and proximity of the heating element as at 16 to blood vessels.These vessels will tend to perform as inherent cooling mechanisms.Accordingly, while attempting to achieve an effective heat therapy, theauto-regulating implants as at 16 generally have been unable toestablish a necessary precise temperature output for requisitetherapeutic time intervals.

[0126] Now turning to the subject of the physiological consequence ofelevating tissue temperature, studies have been carried out toinvestigate both the component of temperature elevation as well as thetime component within which such asserted higher temperatures aremaintained, i.e., the temporal aspect thereof.

[0127] (30) See: Niemz, M. H., “Laser-Tissue Interactions: Fundamentalsand Applications”, 2^(nd) Edition, Springer, Berlin, GE (2002) p.78.

[0128] Such investigations have established critical temperature andtime relationships which identify the occurrence of irreversible tissuedamage effects. In this regard, looking to FIG. 3, a generalizedsemi-log curve 24 is presented illustrating the temporal relationshipbetween the duration of the application of a given temperature to tissuewith the value of that critical temperature at which irreversible tissuedamage may occur. The system and method of the present invention areconcerned, inter alia, with maintaining the treatment of target tissuevolumes at accurately controlled temperatures for all heat-basedtherapies including hyperthermia. Hyperthermia is a form ofthermotherapy where there is an artificial elevation of the temperatureof a group of cells, a tissue, cell culture, or a whole organism forexperimental or therapeutic purposes. Heating of tissue throughthermotherapy techniques can induce a variety of biologic responses,depending on the intensity of the stress induced. When a tissue isheated, certain cells near the focus of the induced heating mayexperience greater heat shock than cells at a distance from the focus.Therefore, within a tissue being heated, a range of responses may occurat the cellular level. These responses of tissues to hyperthermia can bebroadly categorized. If the heat shock is too mild, there will be nodetectable biologic changes (over the basal level of “heat shock” geneexpression typical in the absence of heat shock). A mild heat shock mayinduce reversible cellular changes, including, for example, reversibledenaturation of proteins, triggering of ion fluxes from various cellularcompartments, activation of existing enzymes, and importantly, inductionof alterations in gene expression.

[0129] A more severe heat shock may irreversibly damage cellularcomponents. Under certain conditions, when a cell is damaged, an orderedprocess, apoptosis, is induced that leads to the death of the damagedcell. Apoptosis is considered a form of “programmed cell death,” andcells undergoing apoptosis often exhibit distinctive morphologicchanges. Apoptosis is also involved in many developmental processes,defensive responses to microbial infection, the homeostasis of cellpopulations (e.g. lymphocytes) and as means of eliminating geneticallydamaged cells, such as cancer cells.

[0130] It is generally accepted that apoptosis is an active, highlyorganized, form of cell death, requiring both RNA and protein synthesis.A classic example is the systematic death of a finite number of cells,131, at a certain stage in the life cycle of the nematode Caenorhabditiselegans, a process controlled by the negative and positive regulation ofspecific genes. As demonstrated by development in C. elegans, certaingenes are involved in the regulation of cell death by apoptosis. Aspecific example is the human gene bcl-2. In certain human follicularB-cell lymphomas, deregulation of the expression of bcl-2 has beenidentified as a cause of the prolonged survival of the lymphoma cells.Altered expression of bcl-2 interferes with the typical programmed celldeath pattern, blocking apoptosis even when hematopoeitic growth factorsare absent.

[0131] Apoptotic cells exhibit a pronounced decrease in cellular volume,modification of the cytoskeleton that results in convolution of thecell, and eventual blebbing of the cell's membrane, compaction ofchromatin and its segregation within the nucleus of the cell. The DNA isdegraded into small fragments, and the apoptotic cell sheds smallmembrane-bound apoptotic bodies which may contain intact organelles. Theapoptotic bodies are phagocytosed (e.g. by macrophages) and the contentsof apoptotic bodies are intracellularly degraded, with little release ofthe contents of the apoptotic cells. In this manner, apoptosis does notinduce a localized inflammatory response.

[0132] Apoptosis is differentiated from necrosis by the general absenceof inflammation. It is a physiological type of cell death, part of ahomeostatic mechanism to maintain an optimal number and arrangement ofcells. In certain physiological conditions, massive apoptosis is notfollowed by necrosis and inflammation, such as the removal ofinterdigital webs during early human development, the regression ofliver hyperplasia following withdrawal of a primary mitogen and cellularloss in the premenstrual endometrium.

[0133] Where thermotherapy is sufficiently severe, cells and tissues areso damaged that cellular integrity is destroyed, or the cellularmachinery is so disabled that the induction of apoptosis does not occur.In contrast to apoptosis, necrosis is a type of cell deathmorphologically characterized by extensive cell loss, which results inthe recruitment of inflammatory cells. In necrosis, injured cells mayexhibit clumping of chromatin, swelling of the cell and organelles(demonstrating a loss of control of ion balance), flocculentmitochondria, and eventual bursting and disintegration of the necroticcell. If necrosis is extensive enough, the architecture of a tissue isdestroyed. Extensive necrosis is characteristic of tissue destructioninduced following severe damage by toxic chemicals, invasivemicroorganisms or ischemia. The wholesale release of cellular componentsinto a tissue itself can trigger a damaging inflammatory response.

[0134] When a tissue is damaged, cells may die by a combination ofapoptosis and necrosis. Many agents capable of inducing necrosis alsoinduce apoptosis. Apoptosis often precedes extensive necrosis, withapoptosis in these situations possibly acting in a self-protectivemanner. When the level of insult to a tissue is too great, necrotic celldeath cannot be avoided. Murine mastocytoma cells have been reported toundergo apoptosis after a moderately severe heat shock, but the samecells die via necrosis when the heat shock exposure is more severe.

[0135] For a comparison of apoptosis and necrosis, see:

[0136] (31) Columbano, A., “Cell Death: Current Difficulties inDiscriminating Apoptosis from Necrosis in Context of PathologicalProcesses in vivo.” Journal of Cellular Biochemistry, 58: 181-190(1995).

[0137] The cellular response to a heatshock has been extensivelystudied. Certain heat shock inducible proteins such as Heat ShockProtein 70 (HSP70), HSP 90 and gp96 are expressed constitutively at lowlevels. During mild to moderate heatshock, cellular proteins may undergoconformational changes. It is this alteration in the structure ofproteins, or other reversible denaturation effects, which are believedto play a role in inducing the heat shock response. (Note that otherstressors, such as nutrient deprivation, release of oxygen radicals, orviral infection may also induce conformational aberrations.) Following aheat shock, mRNA expression of the genes encoding HSP70, HSP 90 andgp96, for example (along with that of other heatshock responsive genes)is induced by activating proteins called “Heat Shock Factors.” Theresponse of two “Heat Shock Factors”, HSFI and HSF-II is triggered bydifferent levels of thermal stress. As an example, HSP70 is thought tobe induced more rapidly than (by either less heat stress, or a shorterduration) HSP90. Therefore, different thermotherapy regimes will inducedifferent panels of heat inducible genes.

[0138] For additional background on the heat shock response see:

[0139] (32) Georgopoulos, C., Welch, W. J. “Role of the Major Heat ShockProteins as Molecular Chaperones.” Annu. Rev. of Cell Biol., 9: 601-634(1993).

[0140] (33) Hendrick, J. P. and Hartl, F. U., “Molecular ChaperoneFunctions of Heat-Shock Proteins.” Annu. Rev. of Biochem., 62: 349-84(1993).

[0141] (34) Lindquist, S., “The Heat Shock Response.” Annu. Rev.Biochem., 55: 1151-91 (1986).

[0142] (35) Matzinger, “Tolerance and Danger: the Sensitivity of theImmune System.” Annu. Rev. Immunol., 12: 991-1044 (1994).

[0143] (36) Morimoto R. I., “Perspective: Cells in Stress:Transcriptional Activation of Heat Shock Genes.” Science 259: 1409-10(1993).

[0144] (37) Morimoto, R. I., et al., “The transcriptional regulation ofheat shock genes: A plethora of heat shock factors and regulatoryconditions.” in Stress Inducible Responses, ed. by Feige et al.,Springer Verlag, Boston pp. 120, 139-163 (1996).

[0145] (38) Parsell, D. A. & Lindquist, S., “The Function of Heat-ShockProteins in Stress Tolerance: Degradation and Reactivation of DamagedProteins.” Annu. Rev. of Genet., 27: 437-496 (1993).

[0146] (39) Schlesinger, M. J., “Minireview: Heat Shock Proteins.”Journal of Biological Chemistry 265: 12111-12114 (1990).

[0147] Initiation of a heatshock will induce conformational changes incellular proteins, and lead to the induction of heat shock genes. HSp70has the ability to bind to proteins, is thought to act as a molecularchaperone, and may use an ATP dependant activity to renaturestress-damaged proteins. It is thought that HSP 70 is involved in aprocess that ‘repairs’ partially denatured proteins. If the nativeconformation of a protein is not restored, then the denatured protein isdegraded. During the degradation process, HSP70 can retain a peptidefragment derived from the degraded protein. In essence HSP 70 may thenchaperone an antigenic peptide fragment of the denatured protein. TheseHSP70 chaperoned fragments are then processed though the cell'sendoplasmic reticulum and Golgi apparatus, and can then appear on thecell surface, presented by MHC-I molecules. Antigens presented on thesurface of a cell can then lead to an immune response being generated tothose antigens.

[0148] In order to have processing of peptide fragments, and presentmentof potentially immunogenic fragments on the cell surface, it isnecessary to have a living cell. An apoptotic cell, since the cellularcontents are degraded (for instance, without presenting antigens on thephagocytitic cell's surface MHC-I molecules), may have lowerimmunogenicity than either a heat shocked, but recovering cell or anecrotic cell.

[0149] Accordingly, with accurate temperature and time controls therapyemploying heat shock protein induction becomes available. Other adjuncttherapies available with accurately controlled thermotherapy are, forexample, release agent systems associated with a heating instigatedrelease, radiation treatment, chemotherapy and radiochemotherapy.

[0150] Some approaches utilized by investigators, in the use ofhyperthermia therapy, have achieved accurate temperature measurement andconsequent control by inserting temperature sensors such as fiber optictemperature sensors, thermocouples or thermistors into the tissueadjacent to or integrally with implanted heaters. These fiberoptic,thermocouple or thermistor-based sensors necessarily are tethered havingone or more electrical or optical leads extending externally or to asurface region of the body each time a hyperthermia therapy isadministered. In the latter regard, the somewhat involved procedureoften must also be repeated a number of times over many weeks or monthsto effect the desired therapeutic results. This becomes particularlyproblematic where the approach is employed in thermal therapy proceduresassociated with the human brain. See generally:

[0151] (40) Hynynen, et al., “Hyperthermia in Cancer Treatment.”Investigative Radiology, 25: 824-834 (1990).

[0152] Referring to FIG. 4, the noted tethered approach to sensinginternal target tissue volume subjected to thermal therapy isillustrated schematically. In the figure, a targeted internal tissuevolume 26 of patient 28 is shown to be under thermotherapy treatment.Thermal energy is applied to the target tissue volume 26 from theheating coil or antenna 30 of an ACF (alternating current field) heatingassembly employing a heating modality as represented at block 32. Theprocedure typically is carried out with a system structuring and controlwhich evokes the sought after heating and thermal distribution at thetarget tissue volume 26. One or more temperature sensors 34 a-34 d areimplanted strategically within the target tissue volume 26. Devices 34a-34 d are “tethered” in that electrical leads 34 a-34 d extendtherefrom through or adjacent to the skin to a temperaturemonitor/controller 38. Controller 38 additionally controls the output ofthe heating assembly 32 as is represented by arrow 40. In general, theheating carried out by the heating unit 32 may be enhanced through theutilization of heating elements implanted within the zone of the targettissue volume 26. A principal limitation of the technique illustrated inconnection with FIG. 4 resides in the requirement that the temperaturesensors 34 a-34 d must be inserted into and accurately positioned withinthe patient 28 each time thermotherapy is carried out and the proceduremay be repeated often; calling for a succession of accurate sensorpositionings. As noted earlier, the somewhat arduous insertion of theheat sensing elements 34 a-34 e becomes particularly intrusivelyundesirable where the procedure is carried out in conjunction with braintumor.

[0153] Should those sensors as at 34 a-34 d not be utilized, thetemperatures reached at the target tissue volume 26 during a procedurecan only be approximated by modeling methods which are subject tosubstantial error due to physical differences in the tissue of givenpatients. In this regard, tissues will exhibit differences invascularity, as well as otherwise assumed average properties. As notedhereinbefore, vascularity functions as a conveyance for heat removal inthe vicinity of the targeted tissue region. For further discussion ofthermal modeling based methods of thermotherapy, reference is made topublication (10) supra.

[0154] The present invention employs temperature sensing unteatheredimplants which are located within a target tissue volume, whereupon,using any of the above-discussed extra body heating systems theunteathered implants will provide a quite accurate readout ofpreselected temperature levels. These temperature sensing implants areconfigured as passive resonant circuits with an inductor component and acapacitor component configured as a resonant circuit. That circuit iscaused to ring at a known unique resonant center frequency while thetissue being monitored is at monitor temperatures below a target Curietemperature. When the predetermined setpoint (Curie-based) temperaturefor the tissue is reached, then the known resonating center frequencyabruptly terminates. This sharp termination of resonance in conjunctionwith the known center frequency is achieved by utilizing an inductorcomponent comprised of a winding and a ferromagnetic core. Theferromagnetic core is formulated to evoke a Curie transition, forexample, in magnetic permeability over relatively narrow temperatureranges, for instance, between about 0.1° C. to about 5° C. for use withsensors and as narrow as about 0.1° C. to about 1° C. for use withauto-regulating heaters. This transition in terms of relative magneticpermeability μ_(r), will be from about 100 to 1 to about 5000 to 1.

[0155] A highly advantageous aspect of this inductor component whenemployed with a passive resonant sensor resides in a stabile maintenanceof the resonant center frequency of the sensors during the transitionapproaching the Curie temperature setpoint. During the transition, whilethe intensity amplitude of the sensor output diminishes, its selectresonant center frequency persists. As a consequence, a targettemperature predictive form of control is made available. In general,control is based upon a predetermined ratio of the instantaneous valueof a signal representing the amplitude of the detector signal at theunique resonant center frequency to the maximum detector amplitudewitnessed.

[0156] Returning to FIG. 2, a representation of thepermeability/temperature characteristic of the inductor componentferrite of the passive resonant sensors is shown at dashed line 40having a knee at 42 and a Curie transition range at arrow pair 44. Asthe relative permeability passes the knee 42 sensor output at its uniqueresonant center frequency will commence to diminish with respect to theamplitude of its intensity. Preferably the Curie transition range willbe from about 1° C. to about 2° C., but may be within a range of about0.5° C. to about 5° C. Should the Curie temperature be, in fact, reachedthe resonant center frequency will shift upwardly, in effect, to anoff-scale value. However, system control preferably is carried outbefore that temperature is reached.

[0157] Where autoregulating heater implants are employed with thesensors of the invention, then the above-noted narrow Curie transistorrange as it is present without inductive influence is desirable. Such anarrow range is represented in FIG. 2 at dashed curve as having a knee48 commencing the Curie transition. The narrow transition range isrepresented at arrow pair 50. Because the sensors are of such smallsize, the methodology of the invention can be employed in connectionwith magnetic resonant imaging (MRI) without adverse consequence.

[0158] The temperature sensing implants may be designed to perform attheir predetermined resonant center frequencies as the targeted tissueheats to a lower threshold setpoint or target level. As that Curietemperature-based threshold setpoint is approached within a Curietransition range, the output intensity of the involved sensor at itsunique resonant center frequency diminishes. When the threshold Curietemperature setpoint is reached, the resonant center frequency, ineffect, shifts to an off-scale value. These lower threshold temperaturemonitoring sensors may be combined with temperature sensing implantswhich experience the sharp Curie transition at an upper limit of tissuetemperature. Accordingly, as the Curie temperature-based limit setpointis approached within a Curie transition range, the output intensity ofthe involved sensor at its unique resonant center frequency diminishes.When the limit Curie temperature is reached, the resonant centerfrequency, in effect, shifts to an off-scale value. Thus, in effect, thedesired thermotherapy temperature range is bracketed.

[0159] The passive resonant sensors with inductors exhibiting the Curietransition characteristic may be employed as threshold temperaturemeasuring implants in conjunction with auto-regulating heatersexhibiting Curie temperatures above the sensor threshold temperaturelevels. Because such heaters require an inductive heating modality theirCurie temperature based transitions ranges will be affected. Howeverwith the noted ferromagnetic materials the Curie temperature transitionswill be within much narrower temperature ranges than heretofore havebeen observed. Looking to FIG. 5, a curve or curves relating relativemagnetic permeability, μ_(r), with temperature again are revealed. Inthe figure, curve 52 shows the performance of this ferromagneticmaterial under the influence of low level applied magnetic fieldintensities. Note the sharp transition approaching Curie temperatureT_(c). Where necessary high level applied magnetic field intensities areutilized with the auto-regulators, an adequate but not as sharp Curietransition occurs as represented at curve 54. In general, in order toavoid interference of the high level applied magnetic field with thetemperature monitoring passive temperature sensors the inductive fieldsare applied intermittently with the interrogation-based monitoring ofthe temperature sensors. This assures the sharp Curie transitionperformance with the temperature sensing implants. Depending upon theconditions involved with a particular thermotherapy procedure, theauto-regulator implants also may be employed with both lower thresholdtemperature determining sensor implants and upper limit temperaturesensing implants. Nonmagnetic metal heating sheaths also may be combinedwith the ferrite cores of the temperature sensors themselves. However,this is not a preferred arrangement inasmuch as the sensor associatedwith a heater sheath will tend to measure the temperature of the heatersheath as opposed to the tissue within which the temperature sensor isembedded. Separate heating components are useful where a more controlledlocalization of target tissue volume heating is called for.

[0160] Now turning to the soft ferromagnetic materials employed with theinductor components of the passive resonant circuit based temperaturesensing implants as well as the auto-regulating heaters, ferrites havebeen considered to be crystalline reaction products of the oxides ofiron and one or more other bivalent metals or bivalent metalliccomplexes. The soft magnetic materials are generally categorized asexhibiting a high inductance, B, for a low field, H.

[0161] Particularly for the predominating hyperthermia based proceduresdescribed herein, the soft ferrites are formulated to derive relativelylow Curie point values within, for instance, a range extending fromabout 39° C. to about 65° C. and more typically within a range extendingfrom about 41° C. to about 50° C. Generically, ferromagnetic materialsexhibit pronounced magnetic effects occurring in atoms and ions and stemfrom only a limited number of metallic elements, to wit: Fe, Co, Ni andcertain rare earths. Alloys or oxides of these materials typically willcontain neighboring ions such as Mn to substantially enhance the atomicspin effect. Zn substitution both increases the magnetic moment of Mnand Ni ferrites and lowers the Curie temperature point of a resultantproduct. Such substitution will be seen to appear in ferriteformulations disclosed herein. The metal ion present in largestconcentration in ferrites is Fe³⁺. Because of its high ionic moment ithas a high potential for controlling magnetic characteristics. Sucheffects are not chemical but crystallographic, being related to latticesite distribution.

[0162] The processes for preparing ferrites have an extensive butrelatively short history. Such processes generally reflect the commongoal of formation of a spinel structure. Starting materials typicallyare oxides or precursors of oxides of the cations and their processinginvolves an interdiffusion of metal ions of a select composition to forma mixed crystal. Ferrite powders have been produced by precipitation anddigestion methods. These powders are blended, calcined and milled and,for the case of spinel ferrites, sintered for a variety of purposesincluding: (a) completing the interdiffusion of the component metal ionsinto a desired crystal lattice; (b) establishing appropriate valencesfor the multi-valent ions by proper oxygen control; and (c) developing adesired microstructure. During this procedure, the materials areconsolidated into a body or component, for example, by die-pressing.

[0163] Referring to FIG. 6, a flow chart is presented describing themost commonly utilized ceramic process for forming manganese zincferrites. As represented at block 60, oxides of the metals are firstblended in a ratio according to the desired composition, here providingfor a desired Curie point characteristic. The oxides are milled, and asrepresented at arrow 62 and block 64, the resulting oxide mixture issubjected to a thermal treatment called calcining wherein ferritematerial is synthesized by a solid state reaction. Generally, this stepis performed in air and only a partial ferrite formation isaccomplished. Next, as represented at arrow 66 and block 68 the calcinedmaterial thus obtained is then milled in order to reduce its particlesize and homogenize the material. This step is commonly performed in asteel ball mill. As represented at arrow 70 and block 72 an organicbinder is usually added at this stage in order to control subsequentsteps of granulating or spray drying and pressing. Next, as representedat arrow 74 and block 76, in the preliminary stage of the sinteringprocess, the pressed ferrite part is subjected to an oxidizingtreatment. The aim of this treatment is to remove the organic binderadded previously which at this stage is burned off by heating theferrite part in air. Next, as represented at arrow 78 and block 80, at alater stage of the sintering process a “soak” is introduced with the aimto restore the oxygen stoichiometry wherein the ferrite part is kept ata high temperature in an atmosphere deficient in oxygen with respect tothat of the stoichiometry ferrite.

[0164] One ferrite exhibiting a sharp Curie point transition of 44.5° C.exhibited the following chemistry:

[0165] Iron 49 wt %

[0166] Zinc 15 wt %

[0167] Manganese 9 wt %

[0168] Oxygen 27 wt %

[0169] In addition, calcium oxide may be added to the above formulationto advantageously increase the electrical resistivity of the ferritematerial to greater than 100 ohm-cm, preferably greater than 500 ohm-cmand more preferably greater than 700 ohm-cm. This serves to increase theamplitude of the signal generated by the resonant circuit of the sensor.

[0170] See generally the following publications:

[0171] (41) Yoshifumi, A., et al., “Preparation and Evaluation ofTemperature Sensitive Magnetic Thin Film With Low Curie Temperature”, T.IEEE Japan, 118-A(2): 158-163 (1998).

[0172] (42) Goldman, “Handbook Of Modern Ferromagnetic Materials”,Kluwer Academic Publishers, Norwell, Mass. (1999).

[0173] Referring to FIG. 7, a schematic representation of the resonantcircuit provided with each temperature sensing passive implant isrepresented generally at 90. Circuit 90 is configured with a ferritecore component 92 having a Curie transition range extending to thetarget or setpoint temperature. Turns 94 of an inductive winding areshown wound about the core 92 to provide an inductive component. Startand end termini of the windings 94 are seen to extend at leads 96 and 98to a series coupling with a capacitor 100. The inductance which may bedesigned for implant 90 may be represented by the following expression:

[0174] L=(const.) μ_(r) AN²/I

[0175] Where L is inductance; μ_(r) is relative permeability;

[0176] A is the cross-sectional area of the core 92;

[0177] N is the number of turns of the winding 94; and

[0178] I is the length of the ferrite core component 92.

[0179] As is apparent, the value of inductance may be developed byadjusting the number of turns, N. When excited by an excitationelectromagnetic field from an extra body location, the circuit 90 willresonate in accordance with the expression:

f₀=1/2π{square root}{square root over (LC)}

[0180] where f₀=the resonant center frequency of the resonant circuit;

[0181] L is inductance; and

[0182] C is capacitance.

[0183] With this arrangement, a plurality of temperature sensingimplants may be developed, each with a unique resonant center frequency.The particular resonant frequency which is utilized in carrying outtemperature sensing of a target tissue volume in general, will fallwithin a range of from about 100 kHz to about 2 MHz. As is apparent fromthe above two expressions, when the circuit 90 is exposed totemperatures approaching the Curie temperature, relative permeabilitywill drop to a value approaching one and, in consequence, the reluctanceof the inductor cast decreases and the associated signal output levelissuing from the sensor decreases by 3-fold to 10-fold or more,indicating that the Curie temperature is close at hand. The aboveexpressions also reveal that the various resonant frequencies employedwith the system can be adjusted by controlling the number of turns 94and the value of capacitance for capacitors as at 100. Accordingly, eachtemperature sensor implant will exhibit its own unique resonant centerfrequency based signature.

[0184] In general, the windings 94 are formed of materials includingcopper, silver, gold, aluminum, platinum or other non-magnetic, lowelectrical resistivity metals or alloys and will exhibit diameterswithin a range of from about 0.001 inch to about 0.020 inch andpreferably from about 0.002 inch to about 0.010 inch; and mostpreferably within a range of about 0.003 inch to about 0.007 inch.Because the temperature sensing implant circuits as at 90 are excitedfrom an extra body applied excitation electromagnetic field generated asa broad spectrum pulse exhibiting an excitation interval, it isdesirable that resonant ringing of circuits as at 90 continue for aninterval extending beyond that excitation interval. To achieve thisringing persistence interval it has been found desirable to configurethe implant circuits as exhibiting a high quality factor, Q. Q is ameasure of the sharpness of a resonant peak at the −3 dB point. The Q ofa series RLC circuit may be expressed as follows: Q=ω₀L/R. Accordingly,it is desirable to maintain lower values of resistance which is a factorin the selection of a particular inductive winding wire diameter. It ispreferred that the inductive windings 94 be in a single layer in orderto avoid a resistance elevating proximity effect. However, in general,between one and about ten layers may be employed. The dimensions for thecore length, l, can vary substantially, for example, within a range offrom about 5 mm to about 100 mm; more preferably from about 5 mm toabout 40 mm; and most preferably, from about 5 mm to about 20 mm.

[0185] Referring to FIG. 8, a schematic and block diagrammaticillustration of the system at hand is presented. Represented generallyat 110, the system is shown to include an excitation antenna 112 locatedin a plane 114 which, in general, will be located beneath the patient. Apassive resonant sensor implant will have been located within the targettissue volume of the patient. An exemplary temperature sensing implantis represented at 116. Extending over and about the implant 116 is asensor antenna 118, having a diameter of about 18 inches. Excitationantenna 112, may, for example, be provided as a single turn of 14 awgwire having a diameter of about 20 inches. Antenna 112 is seen coupledvia cable 120 to the output of an excitation assembly represented atblock 122. Assembly 122 functions to supply an excitation pulse of aboutone microsecond duration from a 1000 volt power supply. Accordingly, theexcitation antenna 112 may carry a 40 amp peak current with a waveshapethat is approximately one cycle of a damped sinusoid. In this regard,note that the high voltage power supply is represented at block 124having a plus output line 126 extending to antenna 112 and a negativeoutput line at 128. A high voltage storage capacitor function, C1 islocated between lines 124 and 128 as represented at line 130. Alsorepresented at line 130 is a small sense resistor function, R1. Line 130also is shown extending to a gate drive transformer 132 which receives agating input at node, A, and functions to gate a high voltage transistorfunction Q1 into conduction. Note that one side of transistor Q1 iscoupled with line 130, while the opposite side, represented at line 133,extends with steering diode D1 to a line 134 coupled to antenna 112.Line 134 additionally extends with steering diode D2 to line 130.

[0186] A gate drive circuitry is represented at block 136 shownconnected to line 132 via line 138 and providing the earlier-notedgating pulse, A. Gate drive circuitry 136 is actuated in response to aforward drive input represented at arrow 140. That input is derived at afiberoptic interface circuit represented at block 142 which is seenresponsive to an optical drive input represented at dashed arrow 144. Aninterface optical output is represented at dashed arrow 146. Inoperation, when a forward drive gating pulse is applied to transistor Q1for about one microsecond current flows from the storage capacitorfunction C1 through excitation antenna 112, then returns through diodeD1, transistor function Q1 and returns to the storage capacitor functionC1. That represents the forward half-cycle of excitation of antenna 112.When transistor Q1 is turned off, current flows through diode D2,through excitation antenna 112 and returns to the capacitor function C1.The result is a single cycle sinewave excitation. Sense antenna 118 isblocked during this excitation interval, inasmuch as the excitationfield generated from excitation antenna 112 will tend to couple withantenna 118. Antenna 118, which may be provided as a paired wire deviceis connected through cable 148 to a detector and control functionrepresented at block 150. Function 150 includes fiberoptic interfacecircuitry represented at block 152. Circuitry 152 is seen to beinteractively associated with optical transmission arrows 144 and 146and is powered as represented at arrow 154 from a low voltage linearpower supply represented at block 156. Power supply 156 additionallypowers a timing and control logic function shown at block 158 asrepresented at arrow 160. Function 158 serves to carry out appropriatelogic including the duration of the excitation pulse, delays before theenablement of antenna 118 and the like.

[0187] Also powered from low voltage linear power supply 156 asrepresented at arrows 162 and 164 is a front-end amplification functionrepresented at 166 and an output amplification function represented at168. The detected signals from sense antenna 118 are both amplified andfiltered following a delay interval occurring subsequent to theexcitation interval. That delay interval permits a sufficient dampeningof the excitation pause so as not to interfere with the resonatingsignals emanating from the sensor implant or implants. Note that cable148 extends to the input of a front-end amplification stage 166. Theoutput of the detector assembly also is seen to be amplified asrepresented at symbol 168. As part of the signal treatment, asrepresented at arrows 170 and 172, the sense antenna output is subjectedto bandpass filtering as represented at block 174 as well as is strippedof any d.c. term. The bandpass evoked by the filtering function 174 willextend from, for example, about 100 kHz to about 2 MHz.

[0188] The amplified sense output is directed, as represented at arrow176 to a data acquisition and control network represented in general atblock 178. This analog signal is sampled at a very high rate with ananalog to digital conversion approach. With this digital approach, thesystem may apply the full power of signal averaging to lower baselinenoise with respect to the associated function of identifying thermalsensor broadcast centerline frequency data. For example, utilizing apoint-by-point approach averaging is carried out and resonant frequencydata is derived. For that purpose, Fourier transform approaches areavailable including the fast Fourier transform (FFT). These functionsare represented at block 178 as a data acquisition block 180, thedigital output of which is represented at arrow 182. Arrow 182 extendsto a data processing algorithmic function represented at block 184. Thisalgorithm is responsive to the center frequency intensity signal anddata representing a corresponding unique resonant electromagneticresponse of an implant temperature sensor to derive implant status dataas detector outputs. These Fourier-type outputs representing a uniqueresonant center frequency will diminish in amplitude as core Curietemperature is approached. A ratio of such dimunition (instantaneous tomaximum amplitude) is used for control and monitoring purposes. Asrepresented at bus arrow 186 and block 188 resultant implant status datais asserted to a graphical user interface or readout assembly to providevisibly discernable information to the operator. Signals to instruct thesystem to commence carrying out an excitation and sensing sequence maybe evolved from the data acquisition function 180. Such signalintroduction is represented at arrow 190.

[0189] Referring to FIG. 9, oscillotraces are presented which werederived from a bench testing of the temperature sensor implants. Five ofthe sensor implants were utilized having a 1.5 mm diameter and a lengthof 20 mm. The sensors were configured to derive outputs with centerresonant frequencies of 400 kHz, 500 kHz, 700 kHz, 800 kHz and 900 kHz.Curie transition temperatures for all but the 500 kHz device were 41°C., the 500 kHz device having a Curie temperatures of 44° C. These fivesensors were located in an array pattern on an approximately 1 cm grid.This grid was located within a water bath having a temperature of 25° C.The bottom of this water bath was located at the plane of an excitationantenna having a diameter of 20 inches and formed of the earlier-noted14 awg wire. The sense antenna was arranged having a diameter of 18inches and was formed of paired turns of 20 awg wire and located 12inches above the excitation antenna. In the figure, the trace at level198 is the current waveform that was used for triggering. However, thewaveform is not visible in the figure. The trace at level 200 is a timedomain representation of the analog amplified output of the senseantenna-based detector system. Level 202 represents a fast Fouriertransform (FFT) of level 200. The scale for level 202 is 500 kHz perdivision. The system also averaged eight acquisitions to derive theseFFTs at level 202. Frequency intensity identifier 204 is the FFTresponse from the 400 kHz sensor. Frequency intensity identifier 205 isthe FFT based response to the 500 kHz based sensor. Frequency intensityidentifier 206 is the FFT based output representation for the 700 kHzbased sensor; frequency intensity identifier 207 is the FFT derivedevaluation of the output of the 800 kHz sensor; and frequency intensityidentifier 208 is the FFT based evaluation of the output of the 900 kHzsensor. A spike at 210 is a spurious anomaly. It was determined thatmoving the array up or down on a Z-axis had an effect on amplitude ofthe FFT outputs but not on the frequency spacing. Likewise moving themin the X and Y directions within the cylinder-defined by the excitationand sense antennae had no effect upon frequency spacing. As the sensorarray was heated the pattern remained very stable until a temperature ofabout 41° C. was reached, whereupon identifiers 204 and 206-208disappeared, however, the identifier 205 remained. Following the aboveexpressions, as the Curie temperature of the sensors is reached,inductance dropped, for example, by a factor of 10. As that occurs, apeak extant, for example, at 400 kHz now becomes a peak at 4 MHz.

[0190] An initial concern in the earlier investigations of the instantsystem was addressed to the slight change in relative permeability whichmay occur when a given implant sensor was approaching or transitioningtoward its Curie temperature. The question was posed as to whether theresonant center frequency position would shift during the temperatureinterval of Curie transition so as to despoil the necessary FFT derivedcenter frequency spacing. As the sensors were heated toward their Curietemperatures, resonant center frequencies remained stable and did notincrease or shift. Looking to FIG. 10A a representation of the FFTamplitudes of four sensors 212-215 having differing resonant centerfrequencies (kHz) is provided. The figure illustrates typicallyencountered FFT relative amplitudes corresponding with the intensity ofthe resonant output of the sensors when at monitoring temperatures wellbelow Curie temperatures.

[0191] Now referring to FIG. 10B the FFT relative amplitudes of the samefour sensors 212-215 are illustrated during the course of a Curietemperature transition. Note that the resonant center frequencies haveremained stable, but the detector output FFTs have diminished inrelative amplitude as the temperatures monitored by the sensorsapproached but did not reach Curie temperature.

[0192] Referring to FIG. 10C, actual sensor performance in a bath ofwater which was heated over a period of time is plotted with respect totemperatures and sensor output signal strength ratio for two sensors. Athermocouple was plotted with each sensor and the time/temperature plotsthereof are shown at curves 216 and 217. Curve 218 plots the signalstrength ratio of a sensor having a 41° C. Curie temperature. Note thatas associated temperature curve 216 rises from a nominal human bodytemperature of about 37° C. the signal strength ratio remains at one atregion 219, then commences to drop; essentially dropping into noise asthe bath temperature closely approached 41° C.

[0193] Curve 220 plots the signal strength ratio of a sensor having a45° C. Curie temperature. Note that as its associated temperature curve217 elevates from a normal human body temperature of about 37° C., thesignal strength ratio remains at one at region 221, then commences todrop, essentially dropping into noise as the bath temperature closelyapproached 45° C.

[0194] The control system associated with this form of sensorperformance measures the initial (FFT) signal amplitude for each sensorwith respect to its unique resonant center frequency. Typically thereresonant center frequencies are separated by about 50 kHz to about 75kHz. The relative amplitude of the Fourier transform based signal ofeach sensor is tracked. When that relative amplitude (representing theratio of the instantaneous amplitude to its initial amplitude)diminishes or drops to a select value, the setpoint temperature isassumed to have been reached. In this regard, the extent of any thermalovershoot is somewhat minimized.

[0195] Amplitude ratio ranges for this control approach may range fromabout 0.2 to about 0.7 and preferably from about 0.3 to about 0.5. Thetemperature value at the commencement of the Curie transition range,i.e., at the knee 42 (FIG. 2) is very reproducible (to within about 0.5°C.) but is slightly lower than the true Curie temperature. A Curietransition range of about 0.1° C. to about 0.5° C. is decreased inconnection with FIG. 2. The preferred transition temperature will beabout 1° C. to about 2° C. lower than Curie temperature.

[0196] Referring to FIG. 11A, the high voltage power supply, switching,and associated gate drive circuitry as described in connection with FIG.8 are illustrated in schematic fashion. In the figure, the high voltagepower supply described earlier at 124 is shown being provided as aswitching power supply 226 having a +12V input at line 228 and providinga positive output at line 230 and a negative output at line 232. Lookingmomentarily to FIG. 11B, the +12V input to device 226 is derived from anoff-board power supply (not shown). That input is imported via aconnector 234 with ground output at line 236 and +12V output at line238, a filtering capacitor C2 being connected between lines 236 and 238.Returning to FIG. 11A, device 226 may be provided, for example, as an“A” Series High Voltage Power Supply model 1A12-P4, marketed byUltravolt, Inc., of Ronkonkoma, N.Y. The output of device 226 at lines230 and 234 may be adjusted at a potentiometer 260. Inasmuch as thepower supply 226 is of a switching variety, it may be desirable toprovide its enablement, for example, only during an excitation intervalor portion thereof. Enablement is provided, for example, at lines 262and 264, by the assertion of a high voltage enable signal input, HV_EN.

[0197] A steering diode D3 is seen positioned within output line 230.Diode D3 functions to block downstream voltages and thus protect device226. Similarly, diode D4 coupled between output lines 230 and 232 withinline 266 protects device 226 against the application of a reversedvoltage. Downstream of device 226 are three energy storage capacitorsC5-C7 corresponding with capacitor function C1. In this regard,capacitor C5 is coupled between output lines 230 and 232 at line 270;capacitor C6 is coupled between those output lines at line 271; andcapacitor C6 is coupled between the output lines at line 272. Line 232extends to one input of a header 274 while opposite output line 230extends to an opposite terminal of that device. Header 274 is connectedwith excitation antenna 112 which is connectable with header 274 atlines 276 and 278. A ballast resistor R3 is coupled within line 230 andfunctions as an inrush current limiter with respect to capacitors C5-C7.Additionally, the high voltage across lines 230 and 232 is monitored atline 280 which is coupled intermediate resistors R4 and R5. Theseresistors correspond with sensor resistor function R1 described inconnection with FIG. 8.

[0198] Monitoring line 280 extends to a voltage monitoring networkrepresented generally at 290. In this regard, line 280 extends to lines292 and 294. Line 294, in turn, extends to the positive input of acomparator 296. Line 292 additionally incorporates a Schottky diode D5.Diode D5 functions to protect the network 290 from overvoltages. Theopposite input to comparator 296 is provided by a precision referencenetwork represented generally at 298 comprised of zener diode D6,capacitor C8 and resistor R6. These components combine to provide areference input at line 300 of, for example, 2.5 volts. The output ofcomparator 296 at line 302 is of an open collector variety and thereforeincorporates a pull-up resistor R7 and noise protecting bypass capacitorC9. Resistors R8 and R9 within line 280 function to provide comparatorhysteresis performance. When the high voltage across lines 230 and 232is at an appropriate level, for example, 1000 volts, a logic high truesignal, HV_OK is generated.

[0199] Looking to that circuitry, gate drive circuitry 136 (FIG. 8)again is represented in general by that identifying numeration. Theexcitation pulse to excitation antenna 112 is of about one microsecondduration and is generated in response to an excite or forward drive (FD)signal asserted at line 304 extending to the input terminal of a driver306 Line 304 is coupled to +5V through pull-up resistor R11 at line 308.Driver 306 is configured with resistor R12 and capacitors C10 and C11 toprovide an excite output at line 310. Inasmuch as the excite signal atline 310 drives an inductive device, a protective Schottky diode D7 isprovided between it and ground. Driver 306 may be provided, for example,as a 14 Amp Low-Side Ultrafast MOSFET Driver, type IXDD414PI, marketedby Ixys Corp., of Santa Clara Calif. Line 310 incorporates resistor R13and extends to the primary side of isolation transformer 132. Thesecondary side of isolation transformer 132 is coupled via line 312 tothe gate of power transistor Q1 and via lines 314 and 316 to itsemitter. The gate drive to transistor Q1 includes a steering diode D8,resistors R16 and R17 and transistor Q2 which functions to causetransistor Q1 to turn off quickly. A zener diode D9 protects the gatedrive from overvoltages, while diode D10 protects the drive transistorfrom reverse voltages.

[0200] Excitation transistor Q1 performs in conjunction with twosteering diodes to apply excitation energy to excitation antenna 112 asdescribed in connection with FIG. 8. Those diodes as well as transistorQ1 are identified with the same numeration as described in connectionwith that figure. In this regard, a collector of transistor Q1 iscoupled via line 318 incorporating steering diode D1 to 3×2 header 274via line 314. The emitter of the excitation transistor is coupledthrough steering diode D2 and resistor R18 to header 274. Line 320extending from header 274 to line 314 completes the excitation circuit.In general, transistor Q1 is turned on for about one microsecond toeffect excitation of excite antenna 112 for one half of a sinusoid. Thetransistor then is turned off to permit generation of the opposite halfcycle.

[0201] Referring to FIG. 11C, a power supply 240 is seen coupled with+12V at line 242 to provide a +5V output at line 244. Lines 246 and 248extend respectively from the GND and OV terminals of device 240 to line250 incorporating filtering capacitor C3.

[0202] Referring to FIG. 11D, connector 252 having inputs at lines 254and 256 and configured with resistor R2 and capacitor C4 providesanother +5V input.

[0203] An interrogation cycle for the system at hand involves an initialexcitation of excitation antenna 112 followed by a short, for example, 2microsecond delay, following which data is acquired from sense antenna118 (FIG. 8). For the instant demonstration, a START or START_FRAMEsignal is derived, for example, from a data acquisition and controlnetwork to commence each of these interrogation cycles. Looking to FIG.11E, the receiver component of a optoisolator as shown at 326 serves toreceive and transfer this START signal via line 328 to line 330. Device326 is configured with capacitor C14 and may be provided, for example,as a 40 kBd 600 nm Low Current/Extended Distance Link Receiver, type HFBR-2533 marketed by Agilent, Corp., of Palo Alto, Calif. Line 330 iscoupled through pull-up resistor R19 to +5V and extends to the input aninverter 332 to provide the START_FRAME signal at line 334.

[0204] Referring to FIG. 11F the START_FRAME signal reappears inconjunction with line 334 extending to an input of a programmable logicdevice (PLD) 340. Representing a component of the control circuit of thesystem at hand, PLD 340 is configured with filter capacitors C15-C18 andreceives a clock input at line 342 from the clock network representedgenerally at 344. Network 344 is comprised of a 1 MHz crystal configuredwith capacitors C19 and C20, resistors R20 and R21 and inverters 348 and350. Inverter 348 is configured with capacitors C21 and clock input line342 incorporates an input resistor R22.

[0205] A start-up reset function is provided by a device 354, which isconfigured with resistor R23 and provides a Clear input signal to PLD340 via line 356. Device 354 may be provided as a Supply-VoltageSupervisor and Precision Voltage Detector, model TL7757CD marketed byTexas Instruments, Inc. of Dallas Tex. PLD 340 further is configuredwith resistors R26 and R27 and is programmable from junction device 358having outputs at lines 360-363, which are coupled with pull-upresistors R28-R34. PLD 340 receives status information, for example, theHV_OK signal at line 302, interlock information and the like and whereoperational criteria are in order, provides a STATUS_OK signal at itsoutput line 366. Additionally, the HV_OK signal is employed to providethe power supply enabling signal, HV_EN at line 368. That signal may bedirected to acquisition and control circuitry and additionally may beemployed to enable power supply 226 as described in connection with line262 in FIG. 11A. In the presence of the status signal line 366 and highvoltage enable signal at line 368, PLD 340 may respond to a START_FRAMEsignal at line 334 to derive the excite or forward drive signal, FD atline 370. It may be recalled that the excite signal is directed to line304 in FIG. 11A. Following an appropriate excitation delay permittingboth the development of the second half cycle of the excitation sinusoidand sufficient damping to permit activation of the detection system, anACQUIRE signal is generated at line 372.

[0206] The STATUS_OK signal from line 366 is optically transmitted tothe acquisition and control features of the system. Looking to the FIG.11G the STATUS_OK signal is seen introduced via line 380 to the input ofan opto-transmitter represented generally at 382. Transmitter 382 may beprovided as a 1 MBd 600 nm High Performance Link Transmitter, modelHFDR-1532 marketed by Agilent, Corp. of Palo Alto, Calif. Line 380 iscoupled to +5V through pull-up resistor R35. Device 382 is configuredwith transistor Q3, light emitting diode D11 and resistors R36-R38.

[0207] In similar fashion the ACQUIRE signal at line 372 (FIG. 11F) isoptically transmitted both to detection circuitry and to control andacquisition circuitry of the system. Looking to FIG. 11H the ACQUIREsignal is asserted via line 384 to the input of an opto-transmitterrepresented generally at 386. Device 386 may be provided as a 40 kBd 600nm Low Current/Extended Distance Link Transmitter type HBR-1533 marketedby Agilent, Corp., of Palo Alto, Calif. The device is seen configuredwith transistor Q3, light emitting diode D12, resistors R39-R41 andcapacitor C22.

[0208] Device 382 optically conveys the STATUS_OK signal to an opticalreceiver for further disposition. Referring to FIG. 12A the STATUS_OKopto-receiver is shown at 390. Device 390 is configured with capacitorC24 and resistor R44 and may be provided as a 40 kBd 600 nm LowCurrent/Extended Distance Link Receiver model HFBR-2533 marketed byAgilent, Corp. (supra). The output of receiver 390 is directed to a linedriver 394 which functions to provide a corresponding STATUS_OK outputat line 396 incorporating resistor R45. Looking momentarily to FIG. 12B,a connector 398 is shown receiving the STATUS_OK signal at line 400 forpurposes of conveying that signal to control and data acquisitionfunctions of the system. Returning to FIG. 12A, device 394 is seen to beconfigured with resistors R46 and R47 and capacitor C25.

[0209] The ACQUIRE signal generated from PLD340 and transmitted viaopto-transmitter 386 is received at opto-receiver 402. Device 402 isconfigured with capacitor C26 and resistor R48 and may be provided as a1 MBd 600 nm High Performance Link Receiver, model HFbR-2532 marketed byAgilent Corp. (supra). The output of device 402 at line 404 is directedto an input of line driver 394 to provide a corresponding output at line406 incorporating resistor R49 and extending to a BNC connector 408.Connector 408 is employed to convey the ACQUIRE signal to control anddata acquisition functions of the system. Note, additionally, that thesame ACQUIRE signal is tapped from line 406 at line 410. Returningmomentarily to FIG. 12B, the ACQUIRE signal is seen to be asserted atline 412 to earlier-described connector 398. Note additionally in thatfigure, that the START OR START_FRAME signal is derived from the controlsystem as represented at line 414.

[0210] Returning to FIG. 12A the START_FRAME signal reappears as beingasserted at line 416. Line 416 is seen coupled through pull-up resistorR50 to +5V and to ground through resistor R56. Line 416 also is coupledvia line 418 to an electrostatic discharge (ESD) and over-voltageprotective device 420. Note that the ACQUIRE and STATUS_OK signals alsoare coupled with device 420 as seen at respective lines 422 and 424.Devices as at 420 may be provided as an SCR/Diode Array for ESD andTransient Over-Voltage Protection, model SP724AH, marketed byLittelfuse, Inc., of Des Plaines, Ill. Line 416 incorporates a resistorR51 and extends to an input of driver 394. The corresponding output fromdriver 394 at line 426 extends to the input of an optical transmitterrepresented generally at 428. Device 428 is configured with a lightemitting diode D14, transistor Q4 and resistors R52-R54 and may beprovided as a 40 kBd 600 nm Lower Current/Extended Distance LinkTransmitter model HFBR-1533 marketed by Agilent, Corp. (supra). Device428 functions to optically convey the START_FRAME signal toopto-receiver 326 described in connection with FIG. 11E.

[0211] Driver 394 further is configured with resistors R55-R59 which arecoupled respectively to input terminals A2-A7 and ground.

[0212]FIGS. 12F and 12D should be considered together in the mannerlabeled thereon. Referring to FIG. 12C, the linear power supplydescribed in connection with FIG. 8 at 156 is identified in general withthat same numeration. Power supply 156 receives line input at connector440. Lines 442 and 444 extending from the connector are operativelyassociated with a current limiting varistor 446. Lines 442 and 448 aswell as line 450 extend to one primary winding component of a step-downtransformer represented generally at 452. Lines 448 and 450 are tappedby respective lines 454 and 456 which, in turn, extend to one primarywinding component of a step-down transformer represented generally at458. In similar fashion, lines 460, 462 and 464 extend to anotherprimary winding component of transformer 452. Line 466 extending fromline 464 and line 460 is coupled to another primary winding component ofstep-down transformer 458.

[0213] Secondary output windings of transformer 452 are coupled vialines 470 and 472 to a full wave rectifier represented generally at 474,the output of which is presented at line 476 in conjunction with groundlevel at line 478. Line 478 is seen connected to ground via line 480. Afilter capacitor C29 extends between lines 476 and 478. Line 476 andline 478 via line 482 extend to a regulator 484 the output of which isdirected to lines 486 and 488. The latter lines are filtered atcapacitor C30 extending between lines 486 and 478. Device 484 may beprovided as a Three-Terminal Positive 15 volt Regulator, model LM78M15CTmarketed by National Semiconductor, Inc. of Santa Clara, Calif. With thearrangement shown, the output at line 488 is a regulated positive 15volts.

[0214] The outputs of the secondary windings of transformer 458 arepresent at lines 490 and 492 which are directed to a full wave rectifierrepresented generally at 494. The positive output of rectifier 494 isprovided at line 496, while the negative output thereof is provided atline 498. Ground level is present at line 500. Line 496 is filtered bycapacitors C31 and C32, while line 498 is filtered by capacitor C33.Line 496 and line 502 extending from line 500 are coupled with a voltageregulator 504. Device 504 provides a regulated +5V output at line 506.Line 506 is filtered by a capacitor C34.

[0215] Now looking to the negative output, line 498 and line 508extending from line 500 are directed to a negative voltage regulator 510which functions to provide a regulated −5V output at line 512. Line 512is filtered by a capacitor C35. Device 510 may be provided as aThree-Terminal Negative 5 volt Regulator, model LM79MO5CT marketed byNational Semiconductor, Inc. (supra).

[0216] Sense antenna 118 as described in connection with FIG. 8 is acomponent of a detector assembly. The cable 148 extending from antenna118 is coupled with a socket shown in FIG. 12C at 520. One side ofantenna 118 is coupled to ground as represented at line 522 extendingfrom socket 520, while the opposite side is coupled with input line 524.Input line 524 extends to the drain of MOSFET transistor Q5. The sourceterminal of device Q5 is coupled via line 524 to the source of anotherMOSFET transistor Q6. The drain of transistor Q6 is coupled with line526. Note that transistors Q5 and Q6 are coupled in complimentaryfashion. These transistors are normally in an off-state and function toblock any excitation energy generated from excitation antenna 112 (FIG.8) which tends to couple into the sense antenna 118. Two suchtransistors interconnected in complimentary fashion are necessitatedinasmuch as their structures incorporate an intrinsic diode functionwhich otherwise would pass a sinusoid half cycle. Gate drive totransistor Q6 is provided at line 528 incorporating gate resistor R58.Simultaneous gate drive is provided to transistor Q5 via line 530incorporating gate resistor R59 and extending to line 528. Line 528extends to the output terminal of a driver circuit 532. The Vcc terminalof device 532 is coupled with earlier-described power supply input line488 while its Vee terminal is coupled via line 534 to line 524 extendingintermediate transistors Q5 and Q6. Line 534 is coupled to groundthrough resistor R60 and filter capacitors C36 and C37 are seen toextend between lines 534 and 488. The C terminal of device 532 iscoupled to ground as represented at line 536 and its input, A, terminalis coupled via line 538 to the drain terminal of MOSFET transistor Q7.Device 532 may be provided as a 2.0 Amp Output Current IGBT Gate DriveOpto-coupler, model HCNW 3120, marketed by Agilent Corp. (supra). It isactuated to gate transistors Q5 and Q6 into conduction upon applicationof the ACQUIRE signal to line 540 extending to the gate of transistorQ7. A pull-up resistor R61 couples line 540 to +5V. Transistor Q2 isconfigured such that its source is coupled to ground as represented atline 542 and its drain terminal is coupled through pull-up resistor R62to +5V. The ACQUIRE signal is derived as represented at line 411 in FIG.12A and is asserted under the control of PLD340 (FIG. 11F) followingabout a two microsecond delay which, in turn follows the one microsecondexcitation of excitation antenna 112 (FIG. 8). With the arrangementshown, line 538 is normally retained in a high logic condition to retaintransistors Q5 and Q6 in an off condition. Application of the ACQUIREsignal to the gate of transistor Q7 draws line 538 to the ground andeffects a gating on of transistors Q5 and Q6. As these transistorsconduct, a sense antenna output signal is conveyed along line 526 whereit is treated by the low pass component of a bandpass filter network.These initial low pass components are represented generally at 544 andare comprised of capacitors C38 and C39 and resistors R63 and R64. Line526 extends to the positive input of a bipolar amplifier 546, which isconfigured with filtering capacitors C40-C45 and provides an output atline 548. The gain of device 546 is established at resistors R65 and R66and its output then is submitted to a high pass filter stage representedgenerally at 550 and comprised of capacitor C48 and resistor R67.Capacitor C48 further functions to remove any d.c. term. Nextencountered resistor R70 provides noise suppression and line 548 is seento be coupled to the positive terminal of bipolar amplifier 552.Amplifier 552 is configured with filtering capacitors C49-C55 and itsgain is established by resistors R71 and R72. The output of device 552at line 554 extends though a low pass filtering stage representedgenerally at 556 and comprised of resistor R73 and capacitor C56. Nextin the treatment sequence is a line driver 558. Configured withfiltering capacitors C57 and C58 device 558 may be provided as anUltra-High-Speed, Low-Noise, Low-Power, Open-Loop Buffer, modelMAX4201ESA, marketed by Maxim, Inc. of Sunnyvale, Calif. The output ofdevice 558 at line 560 is protected as represented at line 562 anddevice 564. In this regard, device 564 may be an SCR/Diode Array for ESDand Transient Over-Voltage Protection model number SP724AH, byLittelfuse, Inc. (supra). Line 560 is seen to extend to a BNC connector566 which functions to connect with data acquisition components of thesystem. As noted above, the bandpass filtering will permit signal entryinto the data acquisition system of from about 100 kHz to about 2 MHz.Resonant frequencies above the latter value tend to lack sufficientpersistence beyond the interval of excitation activity. However, withimproved circuit performance, the upper range, in particular, may beexpanded.

[0217] Referring to FIG. 13 a process flow diagram of the system at handis set forth. Looking to the figure, the process commences asrepresented at block 570 wherein the practitioner and the controllercomponents activate a system START logic. Then, as represented at arrow572 and block 574, the high voltage ENABLE function is activated. Thatsignal is asserted, as described earlier herein in conjunction withlines 368 and 262. With the enablement of the switched power supply 226,as represented at arrow 576 and block 578 a determination is made as towhether the switched power supply has developed sufficient voltagelevel, for example, about 1000 volts. Where that is the case, then asrepresented at arrow 580 and block 582 a variety of interlock checks maybe carried out. For example, the antenna cables, data carrying cablesand interactive information cables must be secure. Where the system isthus correctly configured, then as represented at arrow 584 and block586 PLD340 (FIG. 11F) derives a STATUS_OK signal which, as representedat arrow 588 is conveyed to the controller of the system. Thatcontroller, then as represented at arrow 590 and block 592 conveys aSTART or START_FRAME signal to the system as described in connectionwith line 414 in FIG. 12B. That START_FRAME signal is directed to PLD340(FIG. 11F) which, in turn, develops the excite or FD signal whichfunctions to apply a broad spectrum pulse to excitation antenna 112(FIG. 8). As represented at arrow 594 and block 596, this broad spectrumhalf cycle pulse will have a duration of about one microsecond and willring or oscillate in the manner of a full cycle sinusoid. Accordingly,as represented at arrow 598 and block 600 the system delays for abouttwo microseconds to permit formation of the ending half cycle ofexcitation and to await its relaxation so as to minimize interferencewith the sense antenna. Following this delay, as represented at arrow602 and block 604, PLD340 (FIG. 11F) develops an ACQUIRE signal whichfunctions to enable the detector network as described in conjunctionwith line 540 in FIG. 12A. As represented at arrow 606 and block 608 thesense network is enabled by the gating on of transistors Q5 and Q6.Sense antenna 118 (FIG. 8) then acquires the signals broadcast from theresonating heat sensor implants. As represented at arrow 610 and block612 the analog sensor signal then is submitted to low pass filter 544and, as represented at arrow 614 and block 616 the signal then issubmitted to bipolar amplification as represented at amplifier 546 inFIG. 12B. Next, as represented at arrow 618 and block 620 the analogsignal is submitted to a high pass filtering stage and any d.c. term isstripped. Following this filtering, as represented at arrow 622 andblock 624 the analog signal is again amplified as described at device552 in connection with FIG. 12B. As represented at arrow 626 and block628 the analog signal then is submitted to a low pass filter asdescribed at 556 in FIG. 12B, whereupon, as represented at arrow 630 andblock 632 the signal is introduced to line driver 558. Driver 558 thenfunctions to convey the analog signal to the data acquisition andcontrol features whereupon, as represented at arrow 634 and block 636the analog signal is sampled at an analog to digital conversion stage.As represented at arrow 638 and block 640 the digitized equivalent ofabout 32 to about 500 sample waveforms are compiled and, as representedat arrow 642 and block 644 a point-by-point averaging of those sampledigitized waveforms is carried out and as represented at arrow 646 andblock 648 the averaged waveform data is analyzed to develop resonantfrequency intensity data. The averaging of samples functions to minimizesignal noise during use of the sensors within an animal body. Typicallyabout 150 samples are averaged. In this regard, a sample may requireabout a 20 msec interval. Thus 150 samples will involve about 3 seconds,a time factor which is not long in terms of the thermal inertia of thetissue.

[0218] In general, the intensity will be of a Fourier approach whereinresonant center frequencies and their Fourier-based amplitudes areidentified. Next, as represented at arrow 650 and block 652 controllerlogic is employed to identify the above-discussed relative amplitudes ofthe unique resonant frequencies associated with the sensor implants.Accordingly, a unique sensor resonant frequency is determined to bepresent along with its relative amplitude and is associated with theappropriate implant identifier. In this regard, the sensors may be givena numerical identification for readout purposes. With such status andidentification data, then, as represented at arrow 654 and block 656controller interface logic is employed to develop appropriate digitaldata for providing a readout to the operator. That function isrepresented at arrow 658 and block 660. Preferably, certain of thetemperature sensor implants will have a Curie temperature at a lowerthreshold temperature, for example, 41° C., while others will be at anupper limit temperature, for example, 44° C. The readout informationwill apprise the operator as to whether temperature elevation towardthreshold and upper limit temperatures are underway and whether thethreshold temperatures have been reached or exceeded. With suchinformation, the operator is aware that thermal therapy is underway andits status.

[0219] The discourse now turns to the physical structuring of thetemperature sensing implants. Looking to FIGS. 14 and 14A, a temperaturesensing implant is represented generally at 670. Implant 670 includes aferrite core 672 disposed symmetrically about a core axis 674. Core 672is selected having a Curie temperature exhibiting a desired transitionrange extending to an elected temperature. Such ferrite cores aremarketed, for example, by Ceramic Magnetics, Inc., of Fairfield, N.J. Ina preferred embodiment, disposed over the outward surface of ferritecore 672 is an electrically insulative polyimide internal sleeverepresented generally at 676. Note that the oppositely disposed ends oredges of sleeve 676 as at 678 and 680 extend axially beyond thecorresponding end surfaces 682 and 684 of core 672 to provide supportfor mounting the ferrite core/sleeve subassembly on an conduction coilwinding apparatus. Alternately, the coil may be wound directly onto theferrite core by securing both ends of the core in the induction windingapparatus. The end surface 682 and 684 optionally may be trimmed off,for example, with a scalpel blade prior to further assembly steps. Woundover internal sleeve 676 are the inductive winding turns defining theinductive component of the implant. Winding 686 commences with anaxially extending lead portion 688, the tip 690 of which is bent at a 90angle to provide for electrical contact with the axially disposed side692 of a capacitor 694. The opposite end of the winding 686 extendsaxially beneath the winding wrap to a tip 696 (FIGS. 14B, 14C). Tip 696is bent to define a right angle and is electrically coupled with theaxially disposed side 698 of capacitor 694. Windings 686 are retained inposition by an epoxy adhesive which is biocompatible for long-termimplant within the human body, e.g., Epo-Tek 301 manufactured by EpoxyTechnology, Billerica, Mass. Disposed over the assembly of ferrite core,internal sleeve, inductive winding and capacitor is an electricallyinsulative polyimide outer sleeve 700. Note that the end 702 of sleeve700 extends beyond capacitor 694. Similarly, outer sleeve end 704extends beyond internal sleeve 676. Assembly is completed by potting orfilling the voids within sleeve 700 with the noted biocompatible epoxyadhesive. That epoxy adhesive is represented at 706 in FIG. 13A. As afinal step in the implant fabrication process, its outer surfaces may becovered with a biocompatible coating represented at 708. Coating 708 maybe provided as a Parylene C (polymonochloro-p-xylylene) coating ofthickness ranging from about 0.00025 inch (0.00064 mm) to about 0.010inch (0.254 mm) and preferably between about 0.0005 inch (0.012 mm) andabout 0.001 inch (0.025 mm). These coatings are available fromorganizations such as Specialty Coating Systems, of Indianapolis, Ind.

[0220] Practitioners may find it beneficial to structure the implants asat 670 with an anchoring feature engagable with surrounding tissue toprevent any migration of the implants once implanted. One approach toproviding such an anchoring structure is to extend the outer sleeve 700beyond the outward surfaces of the epoxy potting material 706 andassociated biocompatible conformal coating. For example, an outer sleeve700 extension is represented in phantom at 714 in FIG. 14A extendingoutwardly from implant end surface 716. Similarly, extension of sleeve700 is shown in phantom at 718 extending axially outwardly from implantend surface 720.

[0221] A variety of anchoring structures and techniques are employablewith the implants at hand. FIG. 14 illustrates a resilient wire anchor722 in phantom formed, for example, of a medical grade type 316stainless steel. Anchor 722 is retained against the outer sleeve andassociated conformal coating during an insertion or implantationprocedure. When released from the implanting tool, the anchor willspring outwardly to engaged tissue. Other anchoring approaches aredescribed in U.S. Pat. Ser. No. 10/246,347 (supra).

[0222] Temperature sensing implants as at 670 which are configured toidentify lower threshold tissue temperatures may be combined withauto-regulating ferrite core based heater implants. Those ferrite coreheater implants will be configured to exhibit a Curie temperature, forexample, at an upper limit value above the lower threshold value. Aphysical structuring of such an auto-regulated heater implant isillustrated in connection with FIGS. 15 and 15A, 15B. Looking to thosefigures, the heater implant is represented generally at 730. Device 730is formed having a cylindrically shaped ferrite core 732. Core 732 willexhibit a Curie temperature at an elected upper temperature limit value.Preferably, the ferrite core with exhibit a narrow Curie transitionrange as discussed above in connection with FIG. 5. Core 732 issurmounted by a cylindrical medical grade stainless steel sheath or tube734. The internal diameter of sheath 734 is slightly greater than theouter diameter of cylindrical ferrite core 732 to facilitate themanufacturing procedure. Accordingly, a slight gap of annulusconfiguration is represented at 736. Note that the ends of sheath 734 at738 and 740 extend outwardly along central axis 742 from the respectiveend surfaces 744 and 746 of ferrite core 732. The spaces defined bythese stainless steel sheath extensions is filled or potted with anepoxy adhesive as described above which is biocompatible for long-termimplant within the human body. This epoxy, in addition to filling theoutboard regions, also migrates within the gap 736. When so constructed,the entire implant 730 is coated with a biocompatible conformal layer748 layer such as the earlier-described Parylene. The heater structuresas at 730 also may be configured with a tissue anchoring feature asdescribed, for example, in connection with FIGS. 14, 15C and 15D. Intheir general operation, the heater components are inductively excitedto evoke circumferentially developed currents which effect Joulianheating at monitored temperatures below the elected Curie temperature.See generally publication (9) above.

[0223] Biocompatible stainless steel heater collars or end caps can alsobe combined with extended ferrite cores within thermal sensing implantsas at 670. However, such an arrangement generally is not recommendedinasmuch as the temperature sensing components of the implant will beinfluenced by the Joulian heating of the heater sheaths, as opposed tothe more appropriate responsiveness to surrounding tissue temperature.Combined ferrite-based temperature sensing and heater components aredescribed in detail in the noted application for U.S. Pat. Ser. No.10/246,347.

[0224] Another anchor structure which may be employed with eithertemperature sensing implants as at 670 or auto-regulated heater implantsas at 730 is represented in FIGS. 15C and 15D. Inasmuch as the heaterimplant component shown in these figures is identical to that describedin FIGS. 15, 15A and 15B the same identifying numeration is employed butin primed fashion. For this anchoring embodiment, a nonmagneticbiocompatible somewhat expanded helical spring 750 is embedded withinthe epoxy mass 748′. In this regard, the base 752 of the spring 750 isground so as to remain perpendicular to axis 742′ and the end of thespring at 754 is cut square. In general, the epoxy embedded region ofthe spring 750 may be configured with three coils more closelycompressed, for example, having a length of about 0.050 inch and maythen integrally extend to tissue engaging two coils within an axiallength of about 0.120 inch. Anchor 750 may be formed of a nonmagneticstainless steel such as a Type 316 having a diameter ranging from about0.1 mm to about 0.35 mm and preferably between about 0.15 mm to about0.25 mm.

[0225] The implants described in conjunction with FIGS. 14 and 15 may bepositioned in target tissue utilizing a variation of syringe-hypodermicneedle technology. FIGS. 16 and 17 schematically represent one approachto implantation employing such technology. Radiographic, stereotactic,ultrasound or magnetic resonant imaging guidance methods or palpationare procedurally employed to position an implant within a target tissuevolume. Of particular interest, the implants may be positionedintraoperatively as an aspect of open surgical procedures. For instance,a common approach to the treatment of cancer is that of tumor excision.Certain cases, for example, involving colorectal cancer will, upongaining access to the abdominal cavity, reveal a substantiallyinoperative metastasis of the disease. Under such circumstances thesurgical procedure typically is altered to a palliative one, forexample, unblocking the colon and/or the incision is closed and othertreatment modalities are considered.

[0226] However, with the instant system and method, the surgeon is givenan opportunity for deploying hyperthermia-based temperature monitoringand/or heater implants by direct access. Of special interest, colorectalcancers tend to metastasize through the lymph system. Accordingly, theimplants can be intraoperatively positioned within lymph nodes toprovide for the induction of HSPs at the node-retained cancer cells.Other sites of tumor similarly can be implanted. Following surgicalclosure, the hyperthermia therapy procedures described herein can beundertaken in mitigation of the metastasis. In general, practitionersemploying the method herein described with respect to hyperthermia willelect to implant the most or more accessible target tissue volume.

[0227] A target tissue volume is represented in FIGS. 16 and 17 at 780internally within the body 782 of a patient. The syringe-type insertiondevice represented generally at 784 is percutaneously orintraoperatively inserted within the body 782, piercing the skin wherecalled for by virtue of the presence of a sharp tip 786. Needle 786 isfixed to a barrel or finger graspable housing 790 and removably retainsan elongate implant 792 within its internal core proximally from the tip786. Immediately behind the implant 792 within the needle 788 is aplunger rod 794, the lower tip of which at 796 is in free abutmentagainst the outwardly disposed end of implant 792 and which extendsupwardly to a plunger handle 798. As is revealed, particularly withrespect to FIG. 16, once the sharpened tip 786 of the needle 788 hasbeen properly positioned with respect to the target tissue volume 780,then plunger rod 794 and associated handle 798 are stabilizedpositionally with respect to the body 782 and target tissue volume 780,whereupon housing 790 is retracted outwardly to the orientation shown at790′ in FIG. 17. This maneuver releases implant 792 at an appropriatelocation with respect to the target tissue volume 780. Implantationdevices are described, for example, in U.S. Pat. No. 6,007,474.

[0228] Upon the determining of the boundaries or periphery and thephysiological state of a target tissue volume, the practitioner willdetermine the number of implants called for and their positioning withinthe localized tissue region. In effect, the location of the implants canbe mapped such that their resonating responses or lack thereof may beutilized in conjunction with the map to adjust the aiming feature of theexternal heating system. Referring to FIG. 18, the periphery of a targettissue volume is schematically represented at 800. Within this tissueperiphery 800 there are located twelve implants. In this regard, thoseimplants labeled A1-A6 may be temperature sensing implants havinginductors with a Curie temperature core establishing identifiable centerfrequency resonance at monitoring temperatures up to, for example, aCurie temperature of 40° C. As that Curie temperature is approached therelative amplitude of the center frequency will diminish. However, thesecond interspersed grouping of implants as at B1-B6 will incorporateinductors with cores exhibiting a Curie temperature of, for example, 43°C. Accordingly, implants B1-B6 will continue to resonate until thetissue volume within periphery 800 approaches 43° C. During that Curietransition range the relative amplitude of the analyzed resonant centerfrequency will diminish. Accordingly, the practitioner will strive toassure that implants A1-A6 are not resonating in the presence of aresonating output at implants B1-B6. In another embodiment of theinstant system and method, for example, implants B1-B6 may beauto-regulating heater devices as described above having a Curietemperature at the noted 43° C. while implants A1-A6 remain as lowerthreshold temperature sensors having inductors with cores exhibiting aCurie temperature of 40° C.

[0229] Referring to FIG. 19, a somewhat basic implementation of thesystem and method at hand is schematically represented. In the figure apatient is represented at 802 in a supine position on a support 804.Support 804 is formed of a material such as a polymer permittingexcitation energy to be broadcast therethrough. A target tissue volumewithin the body of patient 802 is schematically represented at 806having a distribution of implants as described in connection with FIG.18. For instance, six of the implants may be lower threshold temperaturesensors which will resonate at temperatures approaching a Curietemperature of, for example, 40° C. The second grouping of six sensorswill be structured to resonate at monitor temperatures approaching anupper limit value, for example, a Curie temperature 44° C. Located belowthe support 804 and at a location effective to cause the development ofresonant outputs from the sensor implants is an excitation antenna 808which is depicted as having a cable connection 810 with an excitationelectronics assembly represented at block 812. Excitation electronicsassembly 812 is configured for interactive communication with a receiverelectronics assembly shown at block 814 as represented at dual dashedarrows 816. Arrows 816 may, for instance, be representative ofopto-isolated communication lines. Control to excitation electronicsassembly 812 and receiver electronics assembly 814 is represented byarrow 818 and a controller as represented at block 820. A sense antennais represented schematically at 822. Antenna 822 may be flexible andessentially conform over or drape over the patient 802 in surroundingrelationship about target tissue volume 806. The data acquisition andanalysis components of controller 820 communicate as represented atarrow 824 with a readout schematically represented at 826. Readout oruser interface 826 includes an on/off switch 828 and a measurementfrequency input switch 831. The upper readout of device 826 at 830includes an indicator apprising the operator of the lower thresholdtemperature elected for the therapy as represented at 832. In thisregard, the indicator 832 shows a temperature of 40° C. as being theCurie temperature of the inductor component ferrite core of siximplants. Below the indicator 832 are two linear arrays of visablyperceptible readouts implemented, for example, as light emitting diodes(LEDs). The upper array of LEDs is represented at 834 and is configuredwith six blue output LEDs each associated with a number which will beilluminated in the presence of monitoring temperatures below andapproaching 40° C., i.e., below Tmin. As shown by the numeric sequenceof identifiers immediately above the LEDs of array 834, each LED isassigned to be illuminated in the presence of the select resonant centerfrequency of a given unique implant now numbered 1-6. Below LED array834 is an LED array 838 comprised of six spaced apart green LEDscorresponding with the numeric array 836 and configured to beilluminated when their corresponding implant will have reached theelected relative amplitude of the processed counter frequency data at atemperature approaching the lower threshold Curie temperature of, forexample, 40° C. Accordingly, the green LEDs of array 838 are illuminatedwhen their corresponding sensor implants are above the lower thresholdtemperature value of 40° C. and are not illuminated at monitortemperatures below that value.

[0230] A lower readout 840 is configured in the same manner as readout830. Lower readout 840 includes a Curie temperature indicator 842representing the programmed upper limit Curie temperature for theremaining six implants, for instance, 43° C. Each of the upper limitimplants will have a unique resonant frequency when interrogated atmonitor temperatures below 43° C. and those unique resonant centerfrequencies will provide relative amplitude data of dimishing value attemperatures approaching that upper limit value. Lower readout 840incorporates six yellow LED implemented visual readout componentsrepresented at linear LED array 844. LEDs within the array 844 willilluminate in a yellow coloration at monitor temperatures below andapproaching the upper limit of 43° C., i.e., below Tmax. Each LED willbe illuminated when its associated implant is resonating at itsdesignated unique center frequency in the presence of monitoringtemperatures below the upper limit temperature, i.e., below Tmax.Aligned below LED array 844 is a red LED array represented generally at848. As before, each of the red indicators within array 848 isassociated with a numerically assigned implant identifier as at numericsequence 846. The LEDs at 848 will be illuminated at monitortemperatures above or closely approaching the upper limit temperature,for example, of 43° C. Above that temperature any so thermallyinfluenced implant will cease to provide the assigned unique resonantcenter frequency.

[0231] The system of FIG. 19 is quite basic and thus calls for activeparticipation on the part of the practitioner or operator. That operatoror practitioner is represented at block 850 providing controls tocontroller 820 as represented at arrow 852 and interacting with thereadout or interface 826 as represented at dashed arrow 854.

[0232] The type of heater unit employed with the instant arrangement isone which employs broadcast frequencies which are non-interfering withthe frequency band employed with the temperature sensing implants athand. In this regard, the heater unit will operate at frequencies above,for instance, 2 MHz. Such heaters, for example, are employed to carryout thermotherapy by applying microwave, radiofrequency or ultrasonicenergy from a variety of antenna components, for example, phased arrayantennae. Such products are marketed, for example, by BSD MedicalCorporation of Salt Lake City, Utah.

[0233] For the instant demonstration operator 850 is shown providinginteraction with a heater control function as represented at arrow 856and block 858. Control 858, in turn, as represented by arrow 860 andblock 862 provides control to such an above-described non-interferenceheater unit. The output is represented at arrows 864-866. The latterarrows extend to blocks 868 and 870 representing antennae of such afocused heating system.

[0234] As is apparent, the operator 850 will wish to effect control ofthe heater unit 862 such that LED array 834 is off, and array 838 is onat upper readout 830, while LEDs of array 844 of the lower readout 840are illuminated and the LEDs of arrays 848 are off. Accordingly, theoperator adjusts to maintain green and yellow LED excitation.

[0235] Looking additionally to FIG. 20, the thermal performance of thearrangement of FIG. 19 is schematically plotted. In this regard, thefigure shows a time domain abscissa and a target tissue volumetemperature ordinate. As the heater unit 862 is turned on, thetemperature of the target tissue volume 806 will gradually increase asrepresented by plot component 872. During this interval, the blue LEDindicators at array 834 will be illuminated as the target tissuetemperature is below the lower temperature threshold level Tmin asrepresented at horizontal dashed line 874. When the temperature level874 is approached, i.e., falls within the Curie transition range with aprogressive dimunition is the processed relative amplitude representingan assigned resonant center frequency, the LEDs of array 834 will turnoff, while those at array 838 will turn on with the noted green color.Typically a relative amplitude dimunition by a factor greater than 2(ratio of 0.5 or less) will trigger the LED performance. Resonant centerfrequencies of the lower threshold based implants at temperatures abovetheir Curie temperatures will shift to a much higher resonant frequencywhich is not detected by the system. The heating control is now underthe judgment of the operator 850 with LED arrays 838 and 844 beingilluminated. During this thermotherapy period of time there may beexcursions toward the upper limit target tissue temperature, Tmax asrepresented at plot component 876 and dashed horizontal line 878. Asthis temperature is approached, pertinent ones of the implants willexhibit a dimunition of the processed relative amplitude representingtheir resonant center frequency and certain or all of the red LEDswithin array 848 will illuminate. The operator then asserts control overthe heater unit 862 to effect a lowering of the target tissuetemperature as represented by plot component 880 and this sequence ofevents may continue for the interval of therapy as represented bysubsequent plot components 882, 884 and 886. With the advantage of thepredictable relative amplitude at center frequencies practitionersshould be able to operate the system at hand such that the temperaturesremain above Tmin at level 874 and below Tmax at level 878.

[0236] Referring to FIGS. 21A-21G a procedural block diagram ispresented corresponding with the basic system described in connectionwith FIGS. 19 and 20. In this regard, operator or practitionerinvolvement is accentuated and non-interfering heater units, forexample, in the ultrasound region are employed. Additionally, theprocedure looks to thermal therapy, which includes not only hyperthermiatherapy but also higher level temperature thermal therapy leading tocell necrosis. The diagram set forth in the figures considers looking tohyperthermia therapy with HSP induction.

[0237] Looking to FIG. 21A, the procedure commences as represented atstart node 890 and line 892 extending to block 894. Block 894 providesfor the election of target therapy temperatures for hyperthermia with aconsideration of HSP induction and a susceptibility to adjunct therapysuch as radiation therapy or chemotherapy. Then, as represented at line896 and block 898, implant sensors are selected based upon thethermotherapy goals. For the instant demonstration, the practitionerwill consider the lower threshold temperature and the upper limittemperature levels. As represented at line 900 and block 902, thepractitioner next accesses the target tissue imaging data concerning itslocation, size and any thermal response attributes such as the degree ofvascularity which the tissue may have. With that data, as represented atline 904 and block 906 the practitioner develops a preliminary placementpattern map with an identification of the sensors with respect to theirresonant center of frequency signatures. In this regard, as representedat line 908 and block 910 the temperature sensor implants are selectedand compiled for ex-vivo testing assuring the presence of a uniqueresonant center frequency at monitoring temperatures which aretemperatures considered to be below the Curie temperature of theirinductor component ferrite core members. Then as represented at line 911and block 912 (FIG. 21B) the data acquisition and control features areloaded with the resonant frequency information and numerical sensorimplant identification. Those components of the control assembly arereferred to as an interrogation assembly. With that data loaded, then asrepresented at line 914 and block 916 the control assembly orinterrogation assembly is operated to carry out an ex-vivo pre-testingof the temperature sensor implants for their resonant center frequencyperformance. This ex-vivo testing then provides for the determinationmade as represented at line 918 and block 920. Harkening to FIG. 19, andassuming six lower threshold and six upper limit implants are employed,then the blue LEDs of array 834 should be illuminated as well as theyellow LEDs of array 844. In the event that one or more of these LEDs isnot illuminated, then as represented by return line 922, the procedurereverts to line 908 and reselection of implant sensors.

[0238] Where the test posed at block 920 is affirmative and all implantsare operational, then as represented at line 924 and block 926 a heatingsystem is elected which performs at frequencies not interfering with theimplant interrogation procedure. As represented at line 928 and block930 an initial or starting heating level for the heating unit electedthen is selected. This level may or may not be adjusted in the course oftherapy. In this regard, as represented at line 932 and block 934 thepractitioner determines what the maximum interval should be to reach thelower threshold temperature at the target tissue volume. This isreferred to as the maximum warm-up interval, t_(wu). Correspondingly, asrepresented at line 936 and block 938 FIG. 21C), the practitionerdetermines what the total therapy duration should be. In this regard, aquanta of heat energy is to be administered to the target tissue volumeas determined by the intensity level of the heating unit and theduration of thermal energy application at temperatures above Tmin.

[0239] With the above basic procedures being completed, as representedat line 940 and block 942 a general or local anesthetic agent isadministered and, as represented at line 944 and block 946 thepractitioner employs ultrasound, stereotatic systems, uprightmammographic guidance or palpation to insert the sensor implants intothe target tissue volume using an appropriate delivery device asgenerally discussed in connection with FIGS. 16 and 17. Placement of theimplants is made in accordance with the preliminary placement pattern ormap. It is recommended that the skin of the patient be marked toindicate the closest location of the implants for purposes of focusingthe heating unit. Following implantation, as represented at line 948 andblock 950 a query is made as to whether the implants are in theircorrect positions. In the event that they are not, then as indicated atline 952 the procedure reverts to line 944 for purposes of carrying outcorrect positioning. Where the implants are in appropriate locationsthen as represented at line 954 and block 956 the practitioner revisesthe placement pattern map if necessary. Additionally, as represented atline 958 and block 960 the practitioner records the skin-carried markerlocation for future reference as well as records all resonantfrequencies and associated sensor identification numbers with respect tothe placement pattern map.

[0240] It may be recalled that these teatherless implants will remain inplace indefinitely and that the patient typically will undergo severaltherapeutic sessions. Accordingly, it is necessary that the implantinformation be recorded. Thus, the next line 962 is shown leading totherapy session procedures as labeled. Each of these procedurescommences as represented at line 964 extending to block 966. At block966, the practitioner reproduces the skin-carried markers if necessary.Next, as represented at line 968 and block 970 the patient is positionedupon a treatment fixture such as a table or chair such that the skinsurface carried markers are clearly visible. Then, as represented atline 972 and block 974, guided by the skin-carried marker, thepractitioner positions the heating assembly output component, forexample, phased array antennae as close as practical to the targettissue volume. Additionally, as represented at line 976 and block 978,again guided by the skin-carried marker, the practitioner positions theexcitation and receiver or sense antennae as close as practical to thetarget tissue volume. In this regard, the sense antenna may be flexibleand, in effect drapes over the body surface of the patient.Additionally, where necessary, as represented at line 980 and block 982all of the recorded unique resonant center frequencies and associatedsensor identification numbers are loaded into the interrogation assemblycontroller or data acquisition system. That interrogation controllerthen is turned on as represented at line 984 and block 986 and theprocedure continues as represented at line 988 to the query at block990. At this time, a determination is made as to whether all appropriatelower threshold and upper limit implants are resonating in response tomonitoring or body level temperature, for example, with respect to FIG.19 a determination is made as to whether the appropriate LEDs withinarray 834 are illuminated as well as the LEDs within array 844. If theyare not, then as represented at line 992 and block 994 the practitioneragain consults the implant map and carries out adjustments of the exciteand sense antennae. The test at block 990 then is reiterated asrepresented at line 996 extending to line 988. Where the interrogationsystem is performing appropriately, then as represented at line 998 andblock 1000 (FIG. 21E) the heating assembly is activated with thepredetermined initial heating power level and, as represented at line1002 and block 1004, a time-out of the maximum warm-up interval, t_(wu)commences. Next, as represented at line 1006 and block 1008 a check isnext made as to whether all appropriate LEDs of arrays 838 and 844 (FIG.19) are illuminated. In the event they are not, then as represented atline 1010 and block 1012 a determination is made as to whether themaximum warm-up time has timed out. In the event that it has not, theprocedure continues as represented at line 1014 to the query posed atblock 1016 again determining whether the LED arrays 838 and 844 areappropriately illuminated. In the event that they are appropriatelyilluminated, the procedure continues as represented at line 1018.

[0241] Returning to block 1008, in the event that all appropriate LEDsof the arrays 834 and 844 are illuminated, then the procedure continuesas represented at line 1020 extending to line 1018. Where the queryposed at block 1012 indicates that the maximum warm-up time has beentimed out, then as represented at line 1022 the program reverts to nodeA, which reappears in FIG. 21F. Looking to the latter figure, line 1024extends from node A to block 1026 providing for practitioner adjustmentof the heating assembly output component position and/or the heatingpower level. Then, as represented at line 1028 the program reverts tonode B which reappears in FIG. 21E in connection with line 1030extending to line 1006.

[0242] Returning to the query posed at block 1016, where LED array 838indicates that the target tissue volume temperature is above the lowerthreshold temperature, Tmin and below the upper limit temperature asrepresented at LED array 846, then the program continues as shown atline 1018 to block 1034 representing the commencement of a session of apredetermined therapy duration. That therapy duration commences to betimed out. Where proper therapy temperatures are not present, theprocedure reverts to node B a represented at line 1032. The programcontinues as represented at line 1036 leading to the query posed atblock 1038 (FIG. 21G) where a determination is made as to whether any ofthe upper limit temperatures has been exceeded as indicated by anillumination of one or more LEDs within the LED array 848 (FIG. 19). Inthe event any such temperature elevation excursions have occurred, thenthe procedure reverts as represented at line 1040 to node A providingfor the carrying out of adjustment of the heating assembly outputcomponent or components and heating power level. In the event of anegative determination with respect to the query posed at block 1038,then as represented at line 1042 and block 1044, a determination is madeas to whether the therapy duration has timed out. In the event that ithas not timed out, then the procedure reverts as represented at line1046 to line 1036. Where the therapy duration has timed out, then asrepresented at line 1048 and block 1050 the heating assembly or unit andthe interrogation assembly or controller are turned off and, asrepresented at line 1052 and block 1054, all therapy data are recordedand as represented at line 1056 and node 1058 the therapy session isended. As noted above, in general, several therapy sessions will beinvolved in carrying out a complete treatment. The unteathered natureand essentially permanent positioning of the implants beneficiallyfacilitates the carrying out of several therapy sessions.

[0243] Where auto-regulating heater implants as described in connectionwith FIGS. 15 and 15A-15D, are employed as the upper temperature limitdevices, then the heating units employed typically will be of aninductive variety. As a consequence, the electromagnetic energybroadcast by them will interfere with the interrogation equipmentemployed in accordance with the invention. Accordingly, an intermittentapproach is utilized wherein the inductive heating assembly is activatedfor a heating interval and then turned-off, whereupon the interrogationassembly is activated. Where this intermitting is carried outautomatically as opposed to the basic system of FIG. 19, then, forinstance, the heating assembly may be enabled for about 100 millisecondsto about 1000 milliseconds and the interrogation assembly then isenabled for a sequential 10 milliseconds to about 100 milliseconds. Thisprovides for almost continuous noise-free interrogation and the offinterval for the heating assembly permits a modicum of accommodation forthermal inertia-based “overshoot” which may be encountered.

[0244] A further effect of the noted inductive interference has beendescribed in connection with FIG. 5. It may be recalled in that figurethat with a high magnetic field intensity applied to the sensors orauto-regulating heaters, the Curie transition range will soften. Howeverby intermitting, the original transition range of the sensorsessentially is maintained.

[0245] A graphic illustration of the intermitting performance of thesystem is provided in connection with FIG. 22. Referring to that figure,it may be noted that the graph is sectioned in terms of time along itsabscissa, while power applied to the target tissue volume and, inparticular, to the heater implant is represented along a left ordinate.The noted power is seen to be identified along ordinate 1066 asextending in value essentially from zero to an initial applied powerP_(a) at an initial power level represented at dashed line 1068. Whileshown in horizontal fashion, the level 1068 may vary in accordance withpower adjustments. The temperature witnessed by the sensor implantsand/or heater implants is shown at ordinate 1070 extending from bodytemperature T_(body) to a lower threshold temperature, Tmin, representedat dashed line 1072 as well as to an upper limit temperature, Tmaxrepresented at dashed line 1074. Related permeability of the corecomponents of the implanted temperature sensors and/or implanted heatersis represented along ordinate 1075 as extending from μ_(MIN) (unityvalue for relative permeability) and extends to generally startingrelative permeability which may fall within a substantial range, forexample to values of about 100 to about 10,000. A maximum relativepermeability level, μ_(N) for the given sensor at hand is represented atdotted horizontal line 1076, while the relative permeability of theferromagnetic core component of the sensors or heaters is represented atdashed curve 1078. Leftward ordinate 1080 extends as an arrow having adashed upper component representing diminished intensity, DI of thesensor output at a stable resonant center frequency as temperatureapproaches Curie point temperature within the Curie transition range.Recall that control is based upon the corresponding relative amplitudes.The arrow extends to lower threshold temperature, Tmin. That ordinateextends upwardly in dashed form at 1082 to represent the substantialresonant frequency shift should Curie temperature be reached for thelower threshold. Implants having a Curie temperature corresponding withthe upper limit level 1074 identified as Tmax are represented at thearrow 1084 having a dashed upper component representing diminishedintensity, DI of the sensor output at a stable resonant center frequencyas temperature approaches Curie point temperature with the Curietransition range. Should level 1078 be reached, then the resonantfrequencies of upper limit temperature sensor components will shiftsubstantially upwardly in value as represented at dashed line 1086.

[0246] Now considering the intermittent activation or duty cycle-definedapplication of power and activation/enablement of the interrogationcomponents, it may be observed that power is represented as initiallybeing applied as shown at power curve 1088 between times t₀ and t₁,representing a power application increment of time δt₁. Following thispower application interval the heating function is turned off for asensing or interrogation time extending between times t₁ and t₂,representing an increment of measurement or sensor interrogation time,δt₂. Because the electromagnetic field applied for sensor interrogationpurposes is relatively low in power, the Curie transition rangecharacteristic elected for the sensors remains quite stable. Recall thediscussion associated with FIG. 5, Note that during the intervals, δt₁and δt₂ the temperature value of the implanted sensor as indexed alongordinate 1070 and shown at dashed curve 1090 commences to rise and isseen to exhibit a modicum of thermal inertia during interrogationinterval δt₂. This power-on-power-off-interrogation sequence continues,for example, a power-on condition being applied between times t₂ and t₃with an interrogation interval occurring between times t₃ and t₄. Asthese power-on and interrogation intermitting cycles continue, curve1090 is seen to rise, eventually approaching the lower thresholdtemperature, Tmin at dashed horizontal line 1072. For illustrativeconvenience, note that the figure is broken following time t₅. Power isindicated as being applied during the heating interval t_(n) to t_(n+1).At the termination of that power application time interval, tn+1, lowerthreshold Curie temperature is approached or achieved at the implantsensor inductor core component and may produce a slight thermalovershoot at 1092 within the acceptable range of temperatures betweendashed lines 1072 and 1074. Note, as this occurs, that a permeabilitycurve for the lower threshold sensor implants at knee 1094 change ofstate is experienced and the relative permeability of the implantedsensor component for this lower threshold drops dramatically essentiallyto a unity value as represented at curve 1078 inflection point 1096occurring at time t_(n+2). Under the ensuing time element, unless thetemperature being sensed by the lower threshold devices drops, forexample, below the lower threshold at dashed line 1072, the relativepermeability of the core of the sensor will remain at a unity level asrepresented at 1098. Should the temperature being sensed by the lowerthreshold component drop in temperature below the lower threshold atdashed line 1072 as represented at point 1100, then as shown atpermeability curve portion 1102, relative permeability abruptly rises,for example, to level 1104. Should the lower threshold temperaturesensor again experience a drop in temperature below the threshold level1072 then as represented at curve portion 1106 relative permeabilityagain will abruptly change toward unity. Assuming that the temperatureremains elevated, the unity value for relative permeability for thelower threshold sensor components will remain at a unity level asrepresented at curve portion 1107. Should the heating unit cause thetarget tissue volume approach or to exceed the upper limit temperatureTmax as represented at point 1108 then a power adjustment is called forto return the temperature to its proper range as represented at curveportion 1110. This results in a lowering of the power applied, Pa′, asrepresented at dashed level 1112.

[0247] Referring to FIGS. 23A-23H a procedural block diagram ispresented detailing the activities undertaken with the intermittentoperation of the system as discussed in connection with FIG. 22. Lookingto FIG. 23A, the procedure commences as represented at node 1120 andline 1122 extending to block 1124. As before, the practitioner electsthe target therapy temperatures, for example, for hyperthermia and aconsideration of HSP induction as well as susceptibility to adjuncttherapies. Next, as represented at line 1126 and block 1128 the implantsare selected for the target therapy temperatures. As before, thepractitioner will consider a lower threshold based temperature sensingdevice as well as an upper limit based device. As represented at line1130 and block 1132, the practitioner accesses target tissue imagingdata concerning the location size and thermal response attributes of thetarget tissue volume. With that information, as represented at line 1134and block 1136 the practitioner develops a preliminary implant placementpattern map with an identification of the sensors and/or auto-regulatingheater implants. This map having been selected, as represented at line1138 and block 1140 the practitioner selects and compiles the sensorssuch as the lower threshold temperature sensors and any upper limittemperature sensor implants to be employed. Ex-vivo testing is carriedout of the temperature sensing implants to determine that they areindeed developing the appropriate resonant center frequencies atmonitoring temperatures below associated Curie point temperature. Next,as represented in FIG. 23B at line 1142 and block 1144 the interrogationassembly or data acquisition components are loaded with the uniqueresonant center frequencies involved and the associated sensor implantidentifications. Next, a testing of the temperature sensor implants iscarried out as represented at line 1146 and block 1148. This testdetermines whether the appropriate resonant center frequencies aredetected at room temperature. That determination is represented at line1150 and the query posed at block 1152. In effect, the test determineswhether the appropriate LEDs of arrays of 834 and 844 are illuminated asdescribed in connection with FIG. 19. In the event one or more of theseLEDs is not illuminated, then as represented at line 1154 the procedurereverts to line 1138. Where all temperature sensor implants areperforming at room temperature, then as represented at line 1156 andblock 1158 an alternating current (ACF) field heating system, forexample, an inductive system is elected and as represented at line 1160and block 1162 an initial power level is selected for the heatingsystem. Next, as represented at line 1164 and block 1166 thepractitioner determines the maximum warm-up interval, t_(wu) forinitially achieving the lower threshold minimum temperature, Tmin. Thepractitioner then determines the therapy session duration attemperatures above the lower threshold and below the upper limit asrepresented at line 1168 and block 1170 (FIG. 23C). With thisaccomplished, as represented at line 1172 and block 1174 a general orlocal anesthetic agent is administered to the patient and, as set forthat line 1176 and block 1178, the target tissue volume is analyzed usingsuch modalities as ultrasound, sterotatic, or upright mammographicguidance or palpation. The temperature sensor implants are located aswell as any auto-regulating heater implants at the target tissue volumein accordance with a preliminary placement pattern or map. Further, theskin surface of the patient's body is marked to identify the implantlocations. As represented at line 1180 and block 1182 a determination ismade as to whether the implants are in the proper location. If animplant is not properly located, then as represented at line 1184 theprocedure reverts to line 1176. With the implants being properlylocated, then as represented at line 1186 and block 1188 any revisionsto the implant pattern map are carried out and the program continues asrepresented at line 1190 and block 1192 where the skin carried markerlocation is recorded for future reference and all resonant frequenciesand associated sensor identification numbers further are recorded.

[0248] As then labeled in conjunction with at line 1193, one or moretherapy sessions are carried out. As noted above, inasmuch as thesensors are unteathered and essentially permanently implanted, multipletherapy sessions can be carried out without a requirement forre-implanting such devices. As multiple therapy sessions are carriedout, the skin carried marker may somewhat disappear. Accordingly, lines1193 and 1194 extend to block 1195 (FIG. 23C) calling for thereproduction of the marker if necessary. Line 1196 and block 1198provide for the positioning of the patient on a table or chair such thatthe marker is clearly visible and properly oriented. That marker, thenas represented at line 1200 and block 1202, is utilized in positioningthe heating assembly output component with respect to the target tissuevolume. Additionally, as represented at line 1204 and block 1206 theinterrogation assembly excitation and receiver or sense antennae areappropriately positioned. As noted above, the sense or receiver antennais configured as being flexible and in effect drapes across thepatient's body. From block 1206, as represented at line 1208 and block1210 if not carried out beforehand, the practitioner loads all uniqueresonant center frequencies into the interrogation assembly controller.Then, as represented at line 1212 and block 1214 a test of theinterrogation system is carried out by initially turning on theinterrogation assembly controller and carrying out excite and sensecycles as represented at line 1216 and block 1218. A determination thenis made as to whether all appropriate LEDs within arrays 834 and 844 asdescribed in conjunction with FIG. 19 are illuminated. In the event thatthey are not so illuminated, then as represented at line 1220 and block1222 the practitioner consults the implant placement map and adjusts theinterrogation antennae appropriately. The procedure then returns to line1216 as represented at line 1224. Where all appropriate LEDs have beenilluminated, the procedure continues as represented at FIG. 23E and line1226 and block 1228 providing for the actuation of the heating assemblywith the initial heating ACF power level for a heating period. At thesame time, as represented at line 1230 and block 1232 timing iscommenced with respect to the warm-up time, t_(wu). At the terminationof the heating period, as represented at line 1234 and block 1236 theheating assembly is turned off and as provided at line 1238 and block1240 the interrogation controller is activated with the generation ofthe earlier-described excite and acquire signal activities. Theseactivities are carried out for an interrogation interval and followingthat interval as represented at line 1242 and block 1244 a query is madeas to whether the lower threshold LED array 838 and upper limit LEDarray as at 844 (FIG. 19) are illuminated to represent that thetherapeutic temperature range has been reached. In the event of anegative determination to this query, then as represented at line 1246and block 1248 a determination is made as to whether the warm-up time,t_(wu) has timed out. In the event that it has not timed out, then asrepresented at line 1250 and block 1252 the query posed at block 1244 isreiterated. Where these LED arrays are illuminated, the procedurecontinues as represented at line 1254. On the other hand, where all ofthe noted LEDs are not illuminated then the procedure continues asrepresented at line 1256 and node A. Note additionally, that in theevent that the warm-up time, t_(wu) indeed has timed out in connectionwith the query at block 1248, then the procedure also extends asrepresented at line 1258 to node A.

[0249] Looking momentarily to FIG. 23F, node A reappears in conjunctionwith line 1260 extending to block 1262 providing for manually adjustingthe heating assembly output component position and/or the heating powerlevel. Next, as represented at line 1264 and block 1266, the heatingassembly is turned on for the noted heating period. As represented atline 1268, the procedure then extends to node B. Node B reappears inFIG. 23E in connection with line 1270 extending to earlier describedblock 1236 providing for turning off the heating unit power followingthe heating period.

[0250] In the event of an affirmative determination with respect to thequery posed at block 1252, then as represented at line 1254 and block1272 the session therapy duration time-out commences. Where the query atblock 1244 indicates that all appropriate LEDs are illuminated, theprocedure extends as represented at line 1274 to line 1254. With thecommencement of therapy duration time-out, as represented at line 1276and block 1278 the interrogation assembly is turned off and asrepresented at line 1280 and block 1282 (FIG. 23H) intermittingcontinues with the turning on of the heating assembly for the heatingperiod. At the termination of that heating period, as represented atline 1284 and block 1286 the heating assembly is turned off and asrepresented at line 1288 and block 1290 the interrogation assembly againis activated. The procedure then continues as represented at line 1292to the query posed at block 1294. Block 1294 questions whether any ofthe LEDs representing a temperature excursion above the upper limit havebeen illuminated, for example, the illumination of any of the LEDs ofarray 848 described in connection with FIG. 19. In the event of anaffirmative determination, then as represented at line 1296 theprocedure reverts to node C. Looking momentarily to FIG. 23H, node Creappears in connection with line 1298 extending to block 1300 providingfor turning off the heating unit. Upon the heating unit being turnedoff, as represented at line 1302 and block 1304. The interrogationassembly is activated and as represented at line 1306 the procedurereverts to node D.

[0251] Node D reappears in conjunction with line 1308 in FIG. 23G. Inthis regard line 1308 extends to line 1292 and the query at block 1294.Where none of the LEDs of array 848 (FIG. 19) are illuminated, then asrepresented at line 1310 the procedure carries out the query posed atblock 1312. At block 1312 a determination is made as to whether thetherapy duration has timed out. In the event that it has not, then theprocedure loops as represented at line 1314 to line 1280. Where atherapy duration has timed out, then as represented at line 1316 andblock 1318 both the heating assembly and interrogation assembly areturned off and, as represented at line 1320 and block 1322 therapy dataare recorded and as represented at line 1324 and node 1326 the therapysession is ended.

[0252] The intermitting approach also can be employed with temperaturesensor implants which respond to identify a lower temperature thresholdand upper limit temperature heater implants as described earlier inconnection with FIGS. 15 and 15A-15D. Inasmuch as the heater implantstypically will require an inductive form of alternating field currentexcitation, intermitting is called for to both avoid interference withthe interrogation procedure. The procedure for carrying out thisintermitting approach with this combination of implants is provided inconnection with FIGS. 24A-24G. Looking to those figures, a procedurecommences with start node 1330 and line 1332 extending to block 1334. Atblock 1334, the practitioner elects target temperatures forthermotherapy and susceptibility to adjunct therapy such as radiationtherapy or chemotherapy. Those target temperatures will involve thenoted lower threshold sensed temperature and the upper limitauto-regulating heater temperature. Next, as represented at line 1336and block 1338 the implant sensors with lower threshold temperatures areselected as well as the auto-regulating heater implants with regulationto the upper limit temperature. Then, as represented at line 1340 andblock 1342 target tissue imaging data is accessed, such data concerninglocation, size and thermal response attributes of the target tissuevolume. As represented at line 1344 and block 1346 the practitionerdevelops a preliminary placement pattern map for the heater implants andtemperature sensor implants within the identified target tissue volume.Upon developing this map, as represented at line 1348 and block 1350 thelower threshold temperature sensing implants are selected and compiledfor ex-vivo testing with respect to room temperature. Additionally, asrepresented at line 1352 and block 1354 the unique resonant centerfrequencies to be used with respect to the lower threshold sensorimplants are loaded into the interrogation assembly and, as representedat line 1356 and block 1358 the interrogation assembly is controlled tocarry out the ex-vivo pre-testing of the lower threshold sensorimplants. This test results in the illumination of appropriate LEDs. Inthis regard, line 1360 extends from block 1358 to block 1362 wherein thequestion is posed as to whether all appropriate Tmin LEDs are on. ThoseLEDs will be, for example, within the array 834 described in conjunctionwith FIG. 19. In the event that the appropriate LEDs are not on, then asrepresented at line 1364 the procedure reverts to line 1348. Where allappropriate lower threshold temperature LEDS have been illuminated, thenas represented at line 1366 and block 1368 an ACF heating system iselected which is suitable for performance with the auto-regulatingheater implants. Such a system typically will be an inductive one. Uponelecting the ACF heating system, then as represented at line 1370 andblock 1372 the initial ACF heating power level is selected. With thatselection, as represented at line 1374 and block 1376 a maximum warm-upinterval to initially achieve the lower threshold temperature isdetermined. As represented at line 1378 and block 1380 (FIG. 24C) adetermination is made as to the length of the session therapy while thetarget volume is at or above the lower threshold temperature. With thatdetermination, as represented at line 1382 and block 1384 a general orlocal anesthetic agent is administered and the temperature sensingimplants and heater implants are located within the target tissue volumeas represented at line 1386 and block 1388. The positioning of theimplants is carried out using ultrasound, stereotactic or uprightmammographic guidance or palpation. Additionally, the patient's skin orthe exterior of the patient's body is marked to indicate the closestlocation of the implants. As represented at line 1390 and block 1392 adetermination is made as to whether the implants are in correctpositions. In the event they are not, then the procedure loops asrepresented at line 1394 to line 1386. Where a determination is madethat the implants are in their correct positions, then as represented atline 1396 and block 1398 a revision of the placement pattern map is madeif it is necessary. Next, as represented at line 1400 and block 1402 themarker location is recorded for future reference as well as all resonantfrequencies and associated lower threshold sensor identifications. Aslabeled in conjunction with line 1404 the patient is now prepared toundergo a number of therapy sessions. Lines 1404 and 1405 extend toblock 1406 (FIG. 24D) providing for the reproduction of the marker ifnecessary. Next, as represented at line 1408 and block 1410 the patientis positioned on the support such that the marker on the patient's skinis clearly observable and the target tissue volume is accessible toheating and interrogation procedures. Next, as represented at line 1412and block 1414 the heating assembly output component is positioned asclose as practical to the target tissue volume. Additionally, asrepresented at line 1416 and block 1418 the excitation and sense orreceiving antennae are located with respect to the target tissue volume.If not accomplished earlier, as represented at line 1420 and block 1422all of the unique resonant frequencies and lower threshold temperatureimplant identifiers are loaded into the interrogation assembly. Next, asrepresented at line 1424 and block 1426 the interrogation assemblycontroller is turned on and a performance of the lower thresholdtemperature sensor implants is evaluated as represented at line 1428 andblock 1430. At block 1430 a determination is made as to whether theappropriate lower threshold LEDs are illuminated. Those LEDs weredescribed in connection with FIG. 19 at array 834. In the event certainor all of those appropriate LEDs are not illuminated, then asrepresented at line 1432 and block 1434 the practitioner consults theimplant placement map and adjusts the excite and/or sense antennae asappropriate and the procedure returns as represented at line 1436 toline 1428. Where all appropriate LEDs have been illuminated, asrepresented at line 1438 and block 1440 (FIG. 24E) the heating assemblyis actuated with initial alternating current field heating power for aheating period. As the heating assembly is activated, as represented atline 1442 and block 1444 timing is commenced for the time to warm-up andthe procedure continues as represented at line 1446 extending to block1448. Block 1448 provides for turning off the heating assembly power,whereupon as represented at line 1450 and block 1452 thecontroller/interrogation assembly is turned on to carry out the exciteand acquire functions. Based upon that interrogation, as represented atline 1454 and block 1456 a determination is made as to whether the lowerthreshold heating level has been reached as determined by theillumination of appropriate ones of LED array 838 (FIG. 19). Where allappropriate such LEDs are not illuminated, then as represented at line1458 and block 1460 a determination is made as to whether the warm-uptime interval has timed out. If it has not, then as represented at line1462 and block 1464 the query posed at block 1456 is reasserted. Whereall appropriate LEDs have been illuminated the procedure continues asrepresented at line 1466 and block 1468 providing for the timing out ofthe session therapy duration. Returning to block 1456 where allappropriate LEDs have been illuminated, then the procedure continues asrepresented at line 1470 to line 1466. Where the determination at block1460 is that the warm-up time interval has expired, then as representedat line 1472 the procedure reverts to node A. Similarly, where thedetermination at block 1464 is that all appropriate LEDs have not beenilluminated the program reverts to node A as represented at line 1474.

[0253] Looking momentarily to FIG. 24F node A reappears in conjunctionwith line 1476 extending to block 1478. Block 1478 provides for themanual adjustment of the heating assembly output component and/orheating power level. Additionally, as represented at line 1480 and block1482 the heating assembly power is turned on for a heating period andthe program continues as represented at line 1484 and node B.

[0254] Returning to FIG. 24E, node B reappears with line 1486 extendingto line 1446.

[0255] With the commencement of session therapy duration time-out asrepresented at block 1468, the procedure turns on the heating assemblyfor the noted heating period as represented at line 1488 and block 1490(FIG. 24G). Following the heating period, as represented at line 1492and block 1494 the heating assembly is turned off and as represented atline 1496 and block 1498 the controller/interrogation assembly is turnedon. The procedure then queries as to whether the session therapyduration has timed out as represented at line 1500 and block 1502. Wherethat is not the case, then as represented at line 1504 the procedurereverts to line 1488. However, where the session therapy has timed out,then as represented at line 1506 and block 1508 the heating assembly andthe interrogation assembly are turned off and, as represented at line1510 and block 1512 therapy data are recorded. With such recordation, asrepresented at line 1514 and node 1516 the therapy session is ended.

[0256] Referring to FIG. 25 the system at hand is illustrated inconnection with a controller exhibiting more elaborate interfacefeatures. Looking to the figure, the patient reappears at 1524 supineupon a support or table 1526 and the target tissue volume is representedat 1528. An excitation antenna 1530 is located beneath patient 1524 inthe vicinity of target tissue volume 1528. Antenna 1538 is operativelyassociated with the excitation electronics assembly represented at block1532 by a cable 1534. Assembly 1532, in turn, is interactivelyassociated with a receiver electronics assembly represented at block1538 by an opto-isolated coupling represented at arrows 1540. Receiverassembly 1538 is coupled with a sense antenna 1542 by cable 1544. Asbefore, antenna 1542 may be flexible and draped upon the surface of thepatient 1524 in the vicinity of target tissue volume 1528. A controlleris represented at block 1546 which is operatively associated withreceiver assembly 1538 and excitation electronics assembly 1532 asrepresented by arrow 1548 and the controller is interactively coupledwith a control console 1550 as represented at arrow 1552. A heater unitis represented at block 1554 having an output represented at arrows1556-1558 extending to output components 1560 and 1562. Heater unit 1554is controlled from a heater control assembly as represented at arrow1564, block 1566 and arrow 1568. Control 1566 is operatively associatedwith the console 1550 as represented by arrow 1570.

[0257] Console 1550 incorporates LED arrays as have beenearlier-described in connection with FIG. 19. Accordingly, those arraysas well as their associated implant identifications are shown with thesame numerical representation but in primed fashion. An on/off switch isrepresented at 1572 in combination with an on/off indicator LED 1574.Maximum warm-up time is inserted by the operator into the system withup-down switches 1575 in association with a time read-out 1576. Where anintermitting type interrogate/heat operation is employed, thecorresponding duty cycle is loaded into the system by actuation ofup-down switches 1577 in conjunction with read-out 1578. Total therapytime also is inserted with up-down switches 1580 which are operated inassociation with read-out 1582. A read-out 1584 provides the operatorwith data as to the therapy time elapsed. Read-out 1584 may be reset atreset switch 1586 and an error/prompt display is provided at 1588. Aheater unit ready green LED is provided at 1590 and a correspondingcontroller ready green LED cueing device is represented at 1592. Therapyis started by actuating switch 1596 and the time to reach the lowerthreshold temperature level elapsing is represented by red LED cueingoutput 1598. At such time as that lower threshold of heating has beenachieved, therapy timing is commenced with a green LED based cue 1600.As LED 1600 is illuminated, therapy time elapsed information at read-out1584 is actuated. At such time as the therapy time elapsed 1584 isequivalent to the therapy time 1582, an LED cue is provided by green LED1602 indicating that therapy is complete. In the course of therapy, thepractitioner may wish to stop the therapy. Accordingly, a stop therapyswitch 1604 is provided with an associated red LED cue representing astop therapy condition at 1606.

[0258] Referring to FIGS. 26A-26J the procedure associated with theenhanced system of FIG. 25 is set forth in block diagrammatic fashion.In FIG. 26A, the procedure is shown to start at node 1612 and line 1614extending to block 1616. Block 1616 provides for the election of thetarget therapy temperatures, for example for hyperthermia with aconsideration of HSP induction as well as adjunct therapies. Followingthis election, as represented at line 1618 and block 1620, implantsensors are selected based upon the target therapy temperatures. Asbefore, this selection may include lower threshold temperature basedimplants and upper limit temperature based implants. As represented atline 1622 and block 1624 the practitioner accesses target tissue imagingdata with respect to its location, size and thermo response attributes.With that data at hand, then as represented at line 1626 and block 1628an implant placement pattern map is developed with the identification ofsensors and their proposed location within the target tissue volume.Next, as represented at line 1630 and block 1632 the sensor implants tobe utilized are selected and compiled for ex-vivo testing. For thispurpose, as represented at lines 1634 and block 1636 (FIG. 26B) theunique resonant center frequencies and identification of the sensorimplants is loaded into the control system. The ex-vivo test then iscarried out as represented at line 1638 and block 1640. As representedat line 1642 and block 1644 a test is carried out to determine that theappropriate LEDs within arrays 834′ and 844′ are illuminated. In theevent the test fails, the procedure reverts as represented at line 1646to line 1630. With an affirmative response to the query posed at block1644, then as represented at line 1648 and block 1650 a heating systemmay be elected with frequencies not interfering with the interrogationassembly. Where such interference may occur, then the intermittent formof operation of the system is called for. Next, as represented at line1652 and block 1654 the practitioner elects an initial heating powerlevel and, as represented at line 1656 and block 1568 a maximum warm-upinterval is determined. That interval is loaded into the system byactuation of up-down switch 1575 in conjunction with readout 1576 (FIG.25). As represented at line 1660 and block 1662 (FIG. 26C) the sessiontherapy duration is determined. That duration will be monitored at suchtime as the lower threshold temperature is reached. Locating theimplants then is commenced as represented at line 1664 and block 1666with the administration of a general or local anesthetic agent followingwhich, as represented at line 1668 and block 1670 the sensor implantsare positioned utilizing guidance techniques in accordance with apreliminary placement pattern and the exterior or skin of the patient ismarked to identify the closest location of the implants. Then, asrepresented at line 1672 and block 1674 a determination is made as towhether the implants are correctly positioned. In the event they arenot, then the procedure returns as represented at line 1676 to line1668. Where implant positioning is correct, then as represented at line1678 and block 1680 the implant placement pattern map is updated ifnecessary. As a final step before commencement of a therapy session, asrepresented at line 1682 and block 1684 the marker location is recordedas well as all resonant center frequencies and associated sensoridentification.

[0259] The patient is now prepared for undertaking one or many therapysessions as labeled in correspondence with lines 1686 and 1687,extending to block 1688 (FIG. 26D) providing for the reproduction of themarker if necessary. Where therapy sessions subsequent to the initialones are at hand, then the practitioner may wish to reconsider theelection of the heating unit; determination of a maximum warm-upinterval; the selection of session therapy duration; and the reloadingof previously recorded unique resonant center frequencies into theinterrogation assembly. As represented at line 1690 and block 1692 thepractitioner selects the interrogate/heat duty cycle if an intermittenttype control is at hand. That selection is made by actuation of up-downswitches 1575 in conjunction with readout 1577 as shown in FIG. 25.Next, as represented at line 1694 and block 1696 the therapy timeelapsed reset button or switch 1586 is actuated. The procedure continuesas represented at line 1698 leading to block 1700 which provides forpositioning the patient on a table or chair and appropriately orientingthe marker, whereupon as represented at line 1702 and block 1704 theheating assembly output component or components are positioned as closeas practical to the target tissue volume. Additionally, as representedat line 1706 and block 1708, utilizing the marker on the patient theexcitation and receiver or sense antennae are positioned with respect tothe target tissue volume. As represented at line 1710 and block 1712 thecontroller then acquires the on and continuity status of theinterrogation assembly. With that information, as represented at line1714 and block 1716 (FIG. 26E) a determination is made as to whether theinterrogation assembly status is ok. In the event that it is not, thenas represented at line 1718 and block 1720 an error cue is presented atdisplay 1588 indicating that the antennae cables to the electronics andcontrol console are not properly attached. Additionally, as representedat line 1722 and block 1724 a prompt is presented at display 1588indicating that cable attachments should be checked and the procedurereturns to line 1714 as represented at line 1726. Where theinterrogation assembly status is ok, then as represented at line 1728and block 1730 green LED 1590 is illuminated. Next, as represented atline 1732 and block 1734 the heating unit is actuated following which,as represented at line 1736 and block 1738, the control system acquireson and continuity status of the heating unit and determines, asrepresented at line 1740 and block 1742, whether that status is ok.Where that status is not ok, then as represented at line 1744 and block1746 an error message is presented at display 1588. Additionally, asrepresented at line 1748 and block 1750 a prompt is presented at display1588 advising the operator to check lead/cable attachments and theprocedure returns to line 1736 as represented at line 1752. Where theheating unit status is ok, then as represented at line 1754 and block1756 green LED 1592 is illuminated. With the above checks being made, asrepresented at line 1758 and block 1760, thermotherapy is started byactuating the “start therapy” button or switch 1596. With thisactuation, as represented at line 1762 and block 1764 (FIG. 26F) theheating underway green LED 1600 is illuminated and the procedurecontinues as represented at line 1766 to the query at block 1768determining whether all of the appropriate LEDs of LED arrays 834′ and844′ are illuminated, indicating that heating is underway but that thelower threshold temperature has not been detected. In the event theseLEDs are not illuminated, then as represented at line 1770 and block1772 the practitioner is prompted to press the stop therapy button orswitch 1604. As this occurs, as represented at line 1774 and block 1776,red LED 1606 is illuminated and, as represented at line 1778, theprocedure extends to node A which reappears with line 1780 extending toline 1702. In the event of an affirmative determination with respect tothe query posed at block 1768, then the procedure continues asrepresented at line 1782 and block 1784. Timing,for maximum warm-upinterval commences and the procedure continues as represented at line1786 and block 1788. At block 1788, the control program queries as towhether the stop therapy button or switch 1604 on the control consolehas been pressed. If it has been pressed, then as represented at line1790 and block 1792 the heating unit is turned off; red LED 1598 isilluminated; and green LED 1600 is turned off. The procedure then, asrepresented at line 1794 and block 1796, determines whether therapy isto be resumed. In the event it is to be resumed, as represented at line1800 and block 1802 the therapy may be resumed for the remainingduration of the maximum warm-up interval or unlapsed therapy time byactuating or pressing the start therapy button or switch 1596. This willcause a turning off of red LED 1598 and as represented at line 1802, theprocedure reverts to node B. Node B reappears in FIG. 26E in conjunctionwith line 1804 extending to line 1758. Where the determination at block1798 is that the therapy is not to be resumed, then as represented atline 1806 and node 1808 the therapy session is ended.

[0260] Returning to block 1788, where the stop therapy button or switchhas not been pressed, then as represented at line 1810 and block 1812 adetermination is made as to whether all appropriate LEDs within array834′ and array 844′ are illuminated. In the event they are not, then asrepresented at line 1814 and block 1816 a determination is made as towhether the maximum time of warm-up has timed out. If the maximum timeof warm-up has timed out, then as represented at line 1818 and block1820, red LED 1598 is illuminated and as represented at line 1822 andblock 1824 an error message and prompt is presented at display 1588 andthe procedure advances to node C as represented at line 1826.

[0261] Looking momentarily to FIG. 26I, node C reappears with line 1828extending to block 1830 which provides for the adjustment of the heatingunit output component position and/or the heating power level. Theprocedure then continues to node D as represented at line 1832. Node Dreappears in FIG. 26G with line 1834 extending to line 1810.

[0262] Returning to the query at block 1816, where the maximum time towarm-up has not timed out, then as represented at line 1836 and block1838 a determination is made as to whether all appropriate LEDs withinarrays 838′ and 844′ are illuminated. In the event that they are not,then the program reverts to node D as represented at line 1840. Wherethose LEDs are appropriately illuminated, the program continues asrepresented at line 1842 extending to block 1844 providing for thecommencement of therapy time-out. Returning to the query at block 1812,where the condition represented at block 1838 obtains, then theprocedure diverts to line 1842 as represented at line 1846.

[0263] Returning to block 1844, where therapy time-out has commenced,then as represented at line 1848 and block 1850 where the heating unitelected is one requiring intermittent heating and interrogation, thenthat form of system activation is utilized in accordance with theinterrogate/heat duty cycle elected in connection with up-down switches1577 and readout 1578. The procedure then continues as represented atline 1852 (FIG. 26H) to the query posed at block 1854. Where any of theLEDs in the array 848′ are illuminated, then as represented at line1856, the program looks to node E. Looking momentarily to FIG. 26J, nodeE reappears in conjunction with line 1858 extending to block 1860. Block1860 provides for turning off the heating unit, whereupon as representedat line 1862 and block 1864, the interrogation assembly is turned-onand, as represented at line 1866 the procedure reverts to node C (FIG.26I).

[0264] Returning to the query at block 1854, where none of thetemperature excursion LEDs at array 848′ are illuminated, then theprocedure progresses as represented at line 1868 and block 1870. Block1870 determines whether or not the therapy duration has timed-out. Inthe event that it has not, then as represented at loop line 1872extending to line 1852, the procedure dwells until such time-out occurs.At such time-out, as represented at line 1874 and block 1876 green LED1602 is illuminated and green LED 1600 is turned off. As represented atline 1878 and block 1880 the heating unit and interrogation assembly areturned off and, as represented at line 1882 and block 1884 therapy dataare recorded and as represented at line 1886 and node 1888 the therapysession is ended.

[0265] Hyperthermia currently is employed for purposes of limitingrestenosis at the location of implanted stents in blood vessels. Ingeneral, such stents, for example, may be utilized in percutaneoustransluminal coronary angioplasty (PTCA) for purposes of avoiding acollapse of arteries subsequent to balloon implemented dilation. Thermaltreatment at the site of the stent will typically fall within atemperature range from about 40° C. to about 45° C. As in otherthermotherapeutic procedures, necessary sensing of temperatureheretofore has been carried out in an invasive manner. Specifically, atransluminal catheter borne thermal sensor is maneuvered within thestent structure in the course of the thermal therapy procedure. As isapparent, such an invasive positioning of the temperature sensor isrequired each time the hyperthermia therapy is performed, a procedurewhich may be called for relatively often. In addition to the risk ofthis invasive positioning of the temperature sensor, the catheterizationof the patient involves a substantial cost. See the followingpublications in this regard:

[0266] (43) Stefanadis, C., et al., “Hyperthermia of Arterial StentSegments by Magnetic Force: A New Method to Eliminate IntimalHyperplasia.” Journal of the American College of Cardiology, 37 (2)Supp. A: 2A-3A (2001).

[0267] (44) See additionally European Patent Application No. EP1036574A1.

[0268]FIGS. 27 and 28 illustrate an initial embodiment for a stentformed of non-magnetic material or material which can be heated from anextra body source, for example, by alternating current field heating andwhich initially incorporates an unteathered temperature sensor which isfixed to it prior to the implantation. Looking to FIGS. 27 and 28, themesh-structured stent is represented generally at 1900 extending about acentral axis 1902. Typically, such stents as at 1900 are formed of anon-magnetic inductively exercisable material, for example, austeniticstainless steel such as type 316, titanium, titanium alloys and nitinol.Non-magnetic materials are utilized inasmuch as they often will belocated within the imaging field of highly magnetic devices such as MRIsystems and the like. Stent structures are described in the followingpublications:

[0269] (45) Interventional Vascular Product Guide, Martin Dunitz, Ltd.,London (1999).

[0270] (46) Handbook of Coronary Stents, 3rd ed., Martin Dunitz, Ltd.,London (2000).

[0271] The mesh-like generally cylindrically-shaped stent 1900 is seento be implanted such that its outwardly disposed contact surface 1904will have been urged into abutting and fixed intimate connection withthe intima of a blood vessel 1906. Fixed to contact surface 1904 at thecentral region of stent 1900 is an unteathered temperature responsiveassembly according to the invention which is represented generally at1908. Component 1908 is configured with the rod-shape of device 670described in connection with FIGS. 14 and 14A-14C. The ferrite core asdescribed at 672 of the component will be formulated to develop a Curietransition at an upper temperature limit as described above. That uppertemperature limit is elected inasmuch as the instant embodiment includesonly one passive device with a signature resonant center frequency.Sensor 1908 may be bonded with the stent 1900 and its securement may befurther assured by the positioning of a biocompatible flexible sheath orband 1910 over the central portion of the stent 1900 and over theoutwardly disposed surface 1912 of the sensor assembly 1908. Band 1910may, for instance, be formed of a biocompatible, non-metallic materialsuch as silicone elastomer, Dacron or Teflon. The arrangement is seen toslightly additionally distend blood vessel 1906 at region 1914. Ifdesired, the sensor assembly 1908 may be mounted in intimate thermalexchange relationship with the stent 1900. Providing a biocompatibleelectrically insulated conformal coating such as the earlier-describedParylene as shown at 1916 in FIG. 28 is beneficial and may promoteadhesion of the sensor 1908 to stent 1900.

[0272] The combined stent and unteathered sensor components discussed inconjunction with FIGS. 27 and 28 also may be utilized to implement athermally activatable drug release feature. Referring to FIGS. 29 and30, a stent represented generally at 1920 with a centrally disposed axis1922 is shown having been implanted within a blood vessel 1924. Attachedto the outer contact surface 1926 of stent 1920 is an unteatheredpassive resonant circuit based sensor component 1928. Sensor component1928 may, as before, be configured as described in connection with FIGS.14 and 14A-14C. Component 1928 may be fixed in thermal exchangerelationship with the contact surface 1926 and further may be coatedwith an electrically insulated conformal biocompatible coating 1930 suchas the earlier-described “Parylene” which functions to aid in thesecurement of the sensor to the stent 1920. This securement is furtherenhanced by a flexible band or sheath 1932 surmounting both the stent1920 and the passive resonant sensor component 1928. Band 1932 may bestructured in the manner of earlier-described band 1910. Note, howeverwith the arrangement of FIGS. 29 and 30 that the inward surface 1934 ofstent 1920 is coated with a thermally activatable drug release coatingas shown at 1936. The release coating will have a thickness which mayfall within the range of about 0.001 inch (0.025 mm) to about 0.20 inch(5.0 mm) and. preferably will fall within a range of from about 0.005inch (0.13 mm) to about 0.10 inch (2.5 mm). Such drugs may be provided,for example, as paclitaxel and the antibiotic Sirolimus as well asanti-thrombogenic agents such as heparin and the like. See the followingpublications in this regard:

[0273] (47) Simonsen, “Percutaneous intervention arena still expandingfor heart disease.” Cardiovascular Device Update 7(5): 1-7 (May 2001).

[0274] (48) “Drug-Coated Stents Poised for Growth”, CardiovascularDevice Update, 7(9): 8-10 (September, 2001).

[0275] The nominal drug release temperature will range from about 39° C.to about 65° C. and preferably from about 41° C. to about 50° C. Drugrelease coating 1936, when non-invasively heated to a drug releasingtemperature, provides a controlled amount of a selected drug at thesitus of the stent 1920 to limit restenosis phenomena. Such a drugrelease process can be repeated at therapeutic intervals which may rangefrom weeks to months to even years. Additionally, the coating may beactivated in the event the patient's symptoms or diagnostic methodsindicate that restenosis is occurring and progressing to the point thattherapeutic intervention is warranted. Where hyperthermia therapy iscombined with drug release activity, more than one passive resonantfrequency based sensor may be employed each being assigned a differentCurie transition temperature.

[0276] The unteathered passive resonant circuit based sensors preferablyare positioned on the outer contact surface of the stent structure,inasmuch as such location provides a factor of safety with respect tothe adhesion of the individual components to that contact surface.Should the coupling be damaged, the sensor components are retained bythe stent structure itself outside of luminal blood flow. In addition,the detectable signal amplitude issuing from the passive resonantcircuit is greater if the sensor is placed on the outside of a metallicstent.

[0277] Two of these resonant circuit based passive sensors may beemployed to provide the earlier-described lower threshold temperaturesensing and upper limit temperature sensing. Additionally, multiplesensors may be employed to provide a redundancy. FIGS. 31 and 32illustrate a stent structure with lower threshold and upper limittemperature value sensors in conjunction with a nonmagnetic stentrepresented generally at 1940. Formed, as before, of a nonmagneticmaterial, stent 1940 is seen disposed about a central axis 1942 and hasa generally mesh-like structuring with an outwardly disposed contactsurface 1944 of generally cylindrical configuration. Unteathered passiveresonant circuit based lower threshold and upper limit temperature levelsensors are shown respectively at 1946 and 1948 coupled to contactsurface 1944 at diametrically opposite locations. As before, each ofthese sensors may be configured in the manner described in connectionwith FIGS. 14 and 14A-14C. The assembly additionally may be coated withan electrically insulative biocompatible material represented at 1950 inFIG. 32. That material, which may be the earlier described “Parylene”functions to enhance the bond between the sensors and the outer contactsurface 1944. Sensors 1946 and 1948 further are secured to the contactsurface 1944 by a flexible band or sheath 1952. Band 1952 is structuredin the manner of the earlier-described band 1910. As before, the instantfigures reveal that the blood vessel 1954 within which stent 1940 ispositioned is diametrically enlarged at regions 1956 and 1958 toaccommodate for the thickness of sensors 1946 and 1948 as well as band1952.

[0278] As noted earlier, essentially all metallic stents which have beenimplanted are formed of nonmagnetic material in view of the potentialinvolvement of highly magnetic imaging systems. As a consequence, thosepre-implanted stents can be retrofitted in vivo with the temperaturesensing aspect of the present invention to enhance noninvasivethermotherapeutic procedures or subsequent treatment of restenosisphenomena. The retrofitting approach, in effect, provides for theinstallation of a temperature sensing component containing a stent-likestructure which is diametrically expandable within the preexistingstent.

[0279] Referring to FIGS. 33 and 34, an asymmetrical retrofitting designis illustrated. In the figure, a nonmagnetic metal mesh stent isrepresented in general at 1962 disposed about a central axis 1964 whichhas been previously implanted within a blood vessel 1966. Note in thisregard that the outwardly disposed surface 1968 of the stent 1962 is incontact with the intima of the vessel 1966. The unteathered passiveresonant circuit based temperature sensor carrying insert or supportmember is seen at 1970 disposed about central axis 1964. Insert 1970 isof generally cylindrical configuration with an interior surface 1972 andexterior surface 1974 to which an unteathered passive resonant circuitbased temperature sensor 1976 is bonded. That bond may establish atemperature exchange relationship between the insert and the stent. Ingeneral, the insert 1970 may be formed with essentially the same meshstructuring and material as present in the previously implanted stent1962. Such mesh structuring is not shown in the figures in the interestof illustrational clarity. FIG. 34 shows that the insert and associatedsensor is coated with a biocompatible coating 1978 which may be providedas the earlier-described “Parylene” material. Additionally, thestructural integrity of the attachment of the sensor 1976 is enhanced bya flexible band 1980. Sensor carrying insert or support member 1970 isinserted within the preexisting stent 1962 using balloon angioplastyprocedures. In order to accommodate for the asymmetrical positioning ofonly a single sensor 1976, the insert member 1970 is structured so thatit is preferentially expandable in the region 1982 immediately beneaththe sensor 1976. Accordingly, upon balloon expansion during theplacement of insert 1970, the region 1982 will expand from an initialinsertion diameter diametrically outwardly against the interior surface1984 of the preexisting stent 1962 to create the crimping expansion ofthe contacting surface of that stent 1962 as represented at region 1982.Preferential expansion of the insert 1970 can be provided by structuringthe stent to be thinner at that region and/or the mesh structure openingsize may be asymmetrically varying.

[0280] Referring to FIGS. 35 and 36, a retrofitting or “stent within astent” approach is illustrated wherein two passive, resonant frequencybased temperature sensors are employed. One such sensor may bestructured with a core component providing a lower threshold Curietemperature and the other an upper limit Curie temperature asabove-described. With such an arrangement, the temperature elevation atthe stent may be bracketed between those two temperature values. In thefigures, a pre-implanted nonmagnetic stent is represented generally at2000. As before, stent 2000 has a mesh-type structure of generallycylindrical configuration disposed about central axis 2002. Thecylindrical outer surface 2004 of stent 2000 is in abutting compressiveengagement with the intima of a blood vessel 2006. In order to carry outa hyperthermia form of treatment for restenosis with the necessarytemperature control, a secondary stent or support member insertrepresented generally at 2008 extending about axis 2002 is formed of anexpandable mesh material, e.g., stainless steel 316, Nitina, ortitanium, and functions to support diametrically oppositely disposedtemperature sensors configured according to the invention andrepresented generally at 2010 and 2012. Sensor 2010 may be configuredwith a ferrite core component having a Curie temperature selected as alower threshold temperature, while sensor 2012 may be configured with aferrite core component exhibiting an upper limit Curie temperature toeffect a noted bracketing control. Similar to the embodiment of FIGS. 33and 34, the insert or support member 2008 is configured with acylindrical wall surface 2014 and an exterior surface 2016 upon whichthe sensors 2010 and 2012 are connected. To enhance this connection, aflexible band 2018 surmounts both the cylindrical exterior wall surface2016 and the sensors 2010 and 2012. FIG. 36 reveals that the insert andassociated sensors are coated with an electrically insulativebiocompatible conformal coating 2020 such as the earlier-described“Parylene”. Insert 2008 also may be structured so that it ispreferentially expandable in the region of each of the sensors 2010 and2012. Upon balloon expansion during the placement of the insert and itssupported sensors the regions 2022 and 2024 will expand from an initialinsertion diameter diametrically outwardly against the interior surface2026 of the preexisting stent 2000 to create the crimping expansion ofthe contacting surfaces. Preferential expansion at those regions can beprovided as described in conjunction with FIGS. 33 and 34. Theearlier-discussed hyperthermia therapy temperature ranges apply to thearrangement of FIGS. 35 and 36. A nominal stent heating temperature of45° C. has been described in publication (44) supra.

[0281] See additionally the following publication:

[0282] (49) Thury, A., et al., “Initial Experience With IntravascularSonotherapy For Prevention Of In-Stent Restenosis; Safety AndFeasibility”, J. of Am. College of Cardiology 37 (2) Supplement A.(2000)

[0283] The instrumentation described in connection with FIGS. 19 and 25in general may be employed for carrying out the heating of nonmagneticstents as described above. Where inductive heating components areutilized then the intermittent form of operation of the system is calledfor. However, U.S. Pat. No. 6,451,044 (supra) describes an ultrasoundheating of a stent formed of an ultrasound absorbtive material. Such astent therefore could be heated while continuous temperature monitoringis carried out. Looking to FIG. 37, the instrumentation and supportequipment discussed in connection with FIG. 25 are illustrated forexemplary purposes in connection with a patient 2030. Patient supportcomponents, heating components and interrogation components which arerepeated from FIG. 25 are shown with the same earlier presentednumerical identification but in primed fashion. Stent 1940 (FIG. 31)reappears adjacent the heart region 2032 of patient 2030. Heatingcomponent 1557′ is located in adjacency with the stent 1940. Excitationcoil 1530′ is located for exciting the temperature sensors of stent1940, while the sense antenna 1542′ is positioned about the region ofthe stent 1940 location. The instantaneous heating power generatedwithin the stent 1940 will generally fall with a range of from 0.20calories/second to about 20 calories/second and preferably will bewithin a range of between about 0.5 calories/second and about 10calories/second. The nominal hyperthermia therapy temperature for stentssuch as at 1940 will fall within a range of from about 39° C. to about70° C. and preferably within a range from about 41° C. to about 50° C.

[0284] Referring to FIGS. 38A-38B and 39A-39H a procedural flow chart ispresented concerning the implanting of stent supported temperaturesensors according to the invention. The procedure is associated with theinstrumentation and equipment described in connection with FIG. 37 andcommences with start node 2040 and line 2042 extending to block 2044.Block 2044 describes the provision of a stent with two or more sensors,one having an inductor core exhibiting a lower threshold Curietemperature and the other having an inductor core exhibiting an upperlimit Curie temperature characteristic such that they bracket atemperature range for hyperthermia treatment of stenosis/restenosis. Asrepresented at line 2046 and block 2048, as an alternative, a supportinsert as described in connection with FIGS. 35 and 36 may be providedhaving the same form of sensor response characteristic. The procedurethen continues as represented at line 2050 and block 2052 providing forthe loading of all unique resonant frequencies into the interrogationassembly. Identification of the sensors is only required where more thantwo are at hand. Next, as represented at line 2054 and block 2056 theinterrogation assembly is utilized to carry out an ex-vivo pre-testingof the two sensors for their resonant performance at room temperature.Accordingly, as represented at line 2058 and block 2060, a query isposed as to whether the appropriate LEDs from arrays 834′ and 844′ areilluminated. In the event that they are not, then as represented at line2062 the procedure extends to node A. Node A reappears with line 2064extending to start line 2042. Where all appropriate LEDs have beenilluminated, then as represented at line 2066 and block 2068 (FIG. 38B)a general or local anesthetic agent is administered and, as representedat line 2070 and block 2072 the sensor containing stent is locatedwithin the patient's blood vessel using conventional stent deliverysystems. Once it is positioned, it is deployed at the target locationand the deployment system is removed. As an alternative, as representedat line 2074 and block 2076 a support member with two associated sensorsaccording to the invention is described in conjunction with FIGS. 35 and36 may be positioned within a previously implanted stent and expandedsuch that it is secured within that preexisting stent. The deploymentsystem then is removed. The procedure then continues as represented atline 2078 and block 2080 providing for the positioning of a marker onthe skin surface of the patient close to the location of the stent.Next, as represented at line 2082 and block 2084 the location of thethus placed marker is recorded for future reference and the two resonantcenter frequencies are recorded for any future reference. As representedat line 2086 and node 2088 the stent positioning phase is then ended.

[0285] Subsequent to the stent positioning phase, the patient will bemonitored for the occurrence of clinically significantstenosis/restenosis. This may be to a requirement for a number ofhyperthermia based treatment sessions which can extend over a lengthyperiod. Referring to FIGS. 39A-39H, and block 2090 of FIG. 39A, suchchecks may be carried out, for instance, using angiography, diagnosticultrasound, ex-ray, or MRI techniques. The procedure then continues asrepresented at line 2092 and block 2094 presenting a query as to whetheror not evidence of stenosis/restenosis is present. In the event that itis not, then as represented at line 2096 and block 2098 such checks arecontinued, the patient's cardiac circulatory function being monitored ona periodic basis. Where evidence of stenosis/restenosis does exist, thenas represented at lines 2100 and 2101, thermal therapy according to theinvention is commenced. Lines 2100 and 2101 are labeled inasmuch as asequence of such sessions may be carried out over an extended intervalof time. Accordingly, certain of the steps undertaken earlier may haveto be repeated. Line 2101 is seen extending to block 2102 providing forthe election of a stent heating system. Next, as represented at line2104 and block 2106 the practitioner elects the initial heating powerlevel for the heating system and, as represented at line 2108 and block2110 determines the maximum warm-up interval, t_(wu) to initiallyachieve the lower threshold designated temperature. Additionally, asrepresented at line 2112 and block 2114 a determination is made as tothe session therapy duration at temperatures at or above the designatedlower threshold temperature and below the upper limit temperature. Asrepresented at line 2116 and block 2118 the marker at the patient's skinmay be relocated at its earlier recorded position if necessary. With themarker available, as represented at line 2120 and block 2122 the patientis positioned on an appropriate treatment support such that the markeris clearly visible to provide for close proximity of the heating systemoutput, for instance, an inductive coil. Thus, as represented at line2124 and block 2126 the heating system output component is placed asclose as practical to the stent with guidance by the marker. Theprocedure then continues as represented at line 2128 and block 2130(FIG. 39B) providing for again utilizing the marker to positionexcitation and receiver or sense antennae as close as practical to thestent. It may be recalled that the sense antenna is quite flexible andmay be draped over the patient's body in the vicinity of the stent.Next, the control system is activated as represented at line 2132 andblock 2134, and, as represented at line 2136 and block 2138, wherenecessary the unique resonant frequencies and, if called for, sensoridentifiers are loaded into the interrogation assembly control function.As represented at line 2140 and block 2142 a selection is made as to theinterrogate/heat duty cycle which may be provided as part of themanufacturer of the system or inputted at up-down switches 1577′ seen inFIG. 37. As represented at line 2144 and block 2146, the practitionerwill actuate or press the therapy time elapsed reset switch or buttonshown in FIG. 37 at 1586′. The procedure then continues as representedat line 2148 and block 2150 providing for testing the interrogationassembly acquiring on and continuity type status information. Theinformation thus acquired, as represented at line 2152 and block 2154(FIG. 39C), a determination is made as to whether the status of theinterrogation assembly is ok. In the event that it is not, then asrepresented at line 2156 and block 2158 an error message is presented atdisplay 1588′ and, as represented at line 2160 and block 2162, a promptis displayed advising the practitioner to check cable attachments,whereupon the procedure reverts to line 2152 as represented at line2164. Where the determination at block 2154 is that the interrogationassembly status is ok, then as represented at line 2166 and block 2168,green LED 1582′ (FIG. 37) is illuminated and the procedure attends tothe testing of the stent heating unit as represented at line 2170 andblock 2172. Upon actuating the heating unit into an on condition, asrepresented at line 2174 and block 2176 the on continuity status of theheating unit is acquired and, as represented at line 2178 and block 2180a determination is made as to whether the heating unit status is ok. Inthe event that it is not, then as represented at line 2182 and block2184 an error message is presented at display 1588′ (FIG. 37).Additionally, as represented at line 2186 and block 2188, a promptmessage advising the practitioner to check lead/cable attachment isprovided at that display. The procedure then reverts to line 2174 asrepresented at line 2190.

[0286] Where the heating unit status is ok, then as represented at line2192 and block 2194, green LED 1590′ (FIG. 37) is illuminated and theprocedure continues as represented at line 2196 and block 2198.Hyperthermia therapy is started by actuating the start therapy switch1596′. Actuating the start therapy button, in turn, effects theillumination of green LED 1600′ as represented at line 2200 and block2202 (FIG. 39D). Next, as represented at line 2204 and block 2206, acheck is made that the appropriate LEDs located within arrays 834′ and844′ are illuminated inasmuch as they are at monitor temperatures. Forthe instant demonstration one LED in each of these arrays will beilluminated. In the event of a negative determination with respect tothe query posed at block 2206, then as represented at line 2208 andblock 2210 the practitioner will actuate the stop therapy switch 1604′and, as represented at line 2212 and block 2214, red LED 1606′ isilluminated and the green LED 1500′ is turned off. The procedure thendiverts as represented at line 2216 to node A. Node A reappears in FIG.39B in connection with line 2218 extending to line 2128.

[0287] Where the query at block 2206 indicates that the appropriate LEDsare illuminated, then as represented at line 2220 and block 2222 thecontrol system commences timing for the maximum time to warm up. Asrepresented at line 2224 and block 2226 a determination is made as towhether the stop therapy switch or button 1604′ (FIG. 37) has beenpressed or actuated. In the event that it has, then as represented atline 2230 and block 2232 the heating unit is turned off, red LED 1598 isilluminated and green LED 1598′ is illuminated and green 1600′ is turnedoff (FIG. 37). Next, as represented at line 2234 and block 2236 thepractitioner determines whether or not therapy is to be resumed. If itis to be resumed, as represented at line 2238 and block 2240 the starttherapy switch or button 1596′ is actuated and red LED 1598′ is turnedoff (FIG. 37). The procedure then reverts to node B as represented atline 2242. Node B reappears at FIG. 39C in conjunction with line 2246extending to line 2196. Where the determination at block 2236 is thattherapy is not to be resumed, then as represented at line 2241 and node2243 the therapy session is ended.

[0288] Returning to FIG. 39D and block 2226, where the stop therapyswitch has not been actuated, then as represented at line 2248 and block2250 (FIG. 39E), a determination is made as to whether appropriate onesof the LEDs in array 838′ and array 844′ are illuminated. Where they arenot, as represented at line 2252 and block 2254 a determination is madeas to whether the maximum time to warm-up interval has timed out. In theevent that it has, then as represented at line 2256 and block 2258, redLED 1598′ is illuminated and, as represented at line 2260 and block 2262error and prompt messages are provided at display 1588′ and theprocedure reverts to node C as represented at line 2264.

[0289] Looking momentarily to FIG. 39G, node C reappears in conjunctionwith line 2266 extending to block 2268. Block 2268 provides foradjusting the heating unit output component position and/or the heatingpower level. The procedure then reverts as represented at line 2270 tonode D.

[0290] Returning to FIG. 39E, node D reappears in association with line2272 extending to line 2248. Where the inquiry posed at block 2254indicates that the maximum warm-up time interval has not timed out, thenas represented at line 2274 and block 2276 the query as posed at block2250 is repeated in a determination as to whether therapy leveltemperatures have been reached. In the event that they have not been soreached, then as represented at line 2278, the procedure reverts toearlier described node D. Where all appropriate ones of the LEDs areilluminated the procedure continues as represented at line 2280.Correspondingly, where the same result is achieved with respect to thequery at block 2250, then the procedure continues as represented at line2282 extending to line 2280. Line 2280, in turn, extends to block 2284indicating the commencement of session therapy time-out with a resultingactivation of therapy time elapsed readout 1584′ (FIG. 37). During thistherapy time, as represented at line 2286 and block 2288, forintermittent performance which typically is employed with stent therapy,the heating unit and interrogation assembly are intermitted or cycled inaccordance with the duty cycle which may have been provided inconjunction with up-down switches 1577′. The procedure then continues asrepresented at line 2290 and block 2292 (FIG. 39F) where a query isposed as to whether an LED in the over-temperature array 848′ isilluminated. In the event that there is such an over-temperature, asrepresented at line 2294 the procedure diverts to node E.

[0291] Looking momentarily to FIG. 39H, node E reappears with line 2296extending to block 2298 providing for turning off the heating unit.Then, as represented at line 2300 and block 2302 the interrogationassembly is turned on and as represented at line 2304, the procedurereverts to earlier-described node C which ultimately returns to node D.

[0292] Returning to FIG. 39F and block 2292, where no temperatureexcursions are at hand, then as represented at line 2306 and block 2308a determination is made as to whether the therapy duration has timedout. If it has not, the procedure dwells as represented by loop line2310 extending to line 2290. Where no temperature excursions are athand, then the procedure continues as represented at line 2312 and block2314 to carry out the illumination of green LED 1602′ and turn off greenLED 1600′ (FIG. 37). Further, as represented at line 2316 and block 2318the heating unit and interrogation assembly are turned off and, asrepresented at line 2320 and block 2322 the therapy data are recorded.Upon completing a recordation of the therapy data, as represented atline 2324 and node 2326 the therapy session is ended.

[0293] The passive resonant circuit based sensor implant of theinvention also may be implemented utilizing an inductive componentexhibiting substantially uniform relative permeability over atemperature range of interest, for example, between 40° C. and 45° C. incombination with a capacitor component which exhibits capacitance valuesas a function of temperature. The involved passive resonant circuit willphysically appear essentially identical to that described in connectionwith FIGS. 7 and 14 and 14A-C. Looking to FIG. 40, an inductor isrepresented generally at 2340 as comprising a ferrite core 2342 aboutwhich are provided the turns 2344 of an inductive winding. These turnss2344 are coupled in series, as represented at leads 2346 and 2348, tothe oppositely disposed plates of a capacitor 2350, the capacitancevalues of which vary with temperature. In this regard, referring to FIG.41 the capacitance exhibited by capacitor 2350 may be represented by thecurve 2354 as it extends between capacitance values C1 and C2 within arange of temperatures, for example, between 40° C. and 45° C. The valueof capacitance is given by the expression:

C=(const.)(εA)/d

[0294] where: C is capacitance;

[0295] ε is the dielectric constant;

[0296] A is plate area; and

[0297] d is the distance between the capacitor plates.

[0298] From that expression it may be seen that the capacitance may bevaried by altering either or both the values d and ε.

[0299] Looking additionally to FIG. 42, curve 2354 is reproduced inconjunction with the relative permeability characteristic of the core2342 as represented at curve 2352. For exemplary purposes, curve 2352 isshown exhibiting a Curie transition at knee region 2356 which may be,for example, 100° C., a temperature level well above the temperaturerange of interest eliciting the variation in capacitance withtemperature. This implant arrangement is not limited therefore to asingle Curie temperature based set point but may provide monitorableresonant frequencies which vary along the curve 2354 since the resonantfrequency, f₀, is inversely proportional to the capacitance, C, asdiscussed earlier.

[0300] Since certain changes may be made in the above-described system,apparatus and method without departing from the scope of the inventionherein involved, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be intrepid asillustrative and not in a limiting sense.

1. The method of evaluating a temperature related physical parameter ata subcutaneous region of an animal body, comprising the steps of: (a)providing one or more passive resonant implants having anelectromagnetic response to an extra body applied excitationelectromagnetic field, said response exhibiting a predetermined resonantcenter frequency or frequencies when said implant is at a monitortemperature or temperatures; (b) providing a detector assembly with anantenna, said detector having a detector output of given amplitude inresponse to antenna detections of said electromagnetic response at saidpredetermined resonant center frequency; (c) positioning said detectorassembly antenna at an extra body location effective for deriving a saiddetector response; (d) positioning said one or more implants in thermaltransfer relationship with said animal body region; (e) applying saidexcitation electromagnetic field from an extra body location for anexcitation interval effective to elicit said electromagnetic response;(f) determining the presence of said monitor temperature or temperatureswithin a resonance time subsequent to said excitation interval incorrespondence with said detector output; and (g) evaluating saidphysical parameter in correspondence with said step (f).
 2. The methodof claim 1 in which: said step (a) provides one or more of said passiveresonant implants, each having an electromagnetic response at a uniqueresonant center frequency when said one or more implants are at a saidmonitor temperature or temperatures, and exhibit a decrease in theintensity of said response at said unique resonant center frequency whenapproaching a target temperature above said monitor temperature ortemperatures.
 3. The method of claim 1 in which: said step (a) providesone or more said passive resonant implants as having a saidelectromagnetic response at a said predetermined resonant centerfrequency when said one or more implants are at a said monitortemperature or temperatures, and exhibit an absence of said response atsaid predetermined resonant center frequency when at a targettemperature which is above said monitor temperature or temperatures. 4.The method of claim 2 in which: said step (f) determines the presence ofsaid target temperature subsequent to said excitation interval incorrespondence with a substantial dimunition of said amplitude of saiddetector output.
 5. The method of claim 1 in which: said physicalparameter is the inflammation of tissue of said body at said region. 6.The method of claim 1 further comprising the steps: (h) providing aheating assembly controllable for the generation of heat at saidsubcutaneous region of the body from an application component locatedexternally of said body; and (i) controlling said heating assembly toelevate the temperature of said subcutaneous region in correspondencewith said detector output.
 7. The method of claim 6 in which: said step(a) provides one or more of said passive resonant implants as having asaid electromagnetic response at a resonant center frequency when saidone or more implants are at a said monitor temperature or temperatures,and exhibit a decrease in the intensity of said response at saidpredetermined resonant frequency when approaching a target temperatureabove said monitor temperature or temperatures.
 8. The method of claim 7in which: said step (f) determines the presence of said targettemperature subsequent to said excitation interval in correspondencewith a substantial dimuniton of said amplitude of intensity of saiddetector output.
 9. The method of claim 7 in which: said step (f)determines the presence of said target temperature subsequent to saidexcitation interval in correspondence with a decrease in the amplitudeof said detector output to a value representing a predetermined ratio ofinstantaneous amplitude to the maximum amplitude present at said monitortemperature or temperatures.
 10. The method of claim 9 in which: saidpredetermined ratio is within a range of about 0.2 to about 0.7.
 11. Themethod of claim 9 in which: said predetermined ratio is within a rangeof about 0.3 to about 0.5.
 12. The method of claim 1 in which: said step(a) provides one or more of said passive resonant implants as anunteathered passive resonant circuit with an inductor defining windingand core component, said core having a relative permeabilitycharacteristic exhibiting a drop in relative permeability toward a unityvalue at a Curie temperature occurring above said monitor temperature ortemperatures and corresponding with said target temperature.
 13. Themethod of claim 1 in which: said step (a) provides one or more of saidpassive resonant implants as an unteathered passive resonant circuitwith an inductor component and a capacitor component, said capacitorcomponent and/or said inductor component exhibiting respectivecapacitance values and/or inductance values corresponding with saidmonitor temperature or temperatures.
 14. The method of claim 1 in which:said step (b) provides said interrogation assembly as deriving saiddetector output as a Fourier transform corresponding with said resonantcenter frequency.
 15. The method of claim 13 in which: said step (a)provides said one or more passive resonant implants as exhibiting asubstantially high Q characteristic to promote a ringing effect withinsaid resonance time.
 16. The method of claim 15 in which: said step (b)provides said detector assembly as deriving said detector output as anaverage of a plurality of signals corresponding with said antennadetections.
 17. The method of claim 7 in which: said step (a) provides afirst said unteathered implant having a said electromagnetic response ata first said resonant center frequency corresponding with monitortemperatures below a threshold temperature and exhibits a decrease inthe intensity of said response when approaching said target temperature,and provides a second said unteathered implant having a saidelectromagnetic response at a second said resonant center frequencydifferent than said first resonant center frequency, corresponding withmonitor temperatures below a limit temperature greater than saidthreshold temperature and exhibits a decrease in the intensity of saidresponse when approaching said limit temperature; said step (d)positions said first and second unteathered implants in thermal transferrelationship with said animal body region; said step (b) provides saiddetector output as a first detector output having an amplitudecorresponding with said first electromagnetic response and a seconddetector output having an amplitude corresponding with said secondelectromagnetic response; and said step (i) controls said heatingassembly to elevate the temperature of said subcutaneous region incorrespondence with said first and second detector outputs and stops ordiminishes said elevation of temperature in correspondence with thesubstantial dimunition of the amplitude of said second detector output.18. The method of claim 7 in which: said step (a) provides a first saidunteathered implant having a said electromagnetic response at a firstsaid resonant center frequency corresponding with monitor temperaturebelow a threshold temperature and exhibits an absence of said responseat and above said target temperature, and provides a second saidunteathered implant having a said electromagnetic response at a secondsaid resonant center frequency different than said first resonant centerfrequency, corresponding with monitor temperatures below a limittemperature greater than said threshold temperature and exhibits anabsence of said response when at or above said limit temperature; saidstep (d) positions said first and second unteathered implants in thermaltransfer relationship with said animal body region; said step (b)provides said detector output as a first detector output correspondingwith said first electromagnetic response and a second detector outputcorresponding with said second electromagnetic response; and said step(i) controls said heating assembly to elevate the temperature of saidsubcutaneous region in correspondence with said first and seconddetector outputs and stops said elevation of temperature incorrespondence with the absence of said second detector output.
 19. Themethod of claim 18 in which: said step (b) provides said detectorassembly as deriving a visibly perceptible threshold cue in the absenceof said first detector output.
 20. The method of claim 17 in which: saidstep (b) provides said detector assembly as deriving a visiblyperceptible threshold cue in correspondence with said substantialdimunition in said amplitude of said detector output.
 21. The method ofclaim 19 in which: said step (b) provides said detector assembly asderiving a visibly perceptible limit cue in the absence of said seconddetector output.
 22. The method of claim 20 in which: said step (b)provides said detector assembly as deriving a visibly perceptible limitcue in correspondence with said substantial dimunition of the amplitudeof said second detector output.
 23. An implant system for evaluating atemperature related physical parameter at a target tissue, comprising:an unteathered passive resonant circuit containing sensor with aninductance defining core component having a relative permeabilitycharacteristic, exhibiting a drop in relative permeability toward aunity value at a Curie temperature transition occurring within atemperature range ΔT_(c), said circuit being responsive to a transientapplied electromagnetic field to resonate at a predetermined resonantcenter frequency at temperatures below said temperature range, ΔT_(c)and exhibiting a dimunition of the intensity of said response at saidresonant center frequency in correspondence with said Curie transitionrange.
 24. The implant system of claim 23 in which said sensor exhibitsan absence of said response at said predetermined resonant centerfrequency at said Curie temperature.
 25. The implant system of claim 23in which said sensor has an externally disposed surface coated with abiocompatible conformal layer.
 26. The implant system of claim 23further comprising at least one tissue engaging implement fixed to andextending outwardly from said sensor and effective to engage tissue inadjacency therewith when implanted.
 27. The implant system of claim 23in which said implant system further comprises: a heater component inheat exchange relationship with said sensor and dimensioned with saidsensor to effect a minimally invasive implantation at said targettissue.
 28. The implant system of claim 23 further comprising athermally activatable release agent coating extending over said sensorand effective to dispense said agent at the situs of said target tissuewhen said target tissue is substantially at said predeterminedtemperature.
 29. The implant system of claim 27 in which said heatercomponent is separate from said sensor and is configured forimplantation within said target tissue in spaced relationship with saidsensor.
 30. The implant system of claim 29 in which the surface of saidheater component supports a thermally activatable release agent coatingeffective to disperse at the situs of said target tissue when saidheater component is at a temperature generally corresponding with saidpredetermined temperature.
 31. The implant system of claim 29 in whichsaid heater component is formed of a non-magnetic metal.
 32. The implantsystem of claim 29 in which said heater component is formed ofultrasound absorbtive material.
 33. The implant system of claim 29 inwhich said heater component further comprises at least one tissueengaging implement fixed to and extending outwardly therefrom andeffective to engage tissue in adjacency therewith when implanted. 34.The implant system of claim 23 in which said sensor further comprises aferrite inductive core component exhibiting a said Curie transitionwithin said temperature range, an inductive winding with turns woundabout said core, and a capacitor coupled to define said resonant circuitwith said inductive winding.
 35. The implant system of claim 23, furthercomprising: a non-magnetic stent having a generally cylindricalconfiguration with an outer surface and central axis, expandablegenerally diametrically from an insertion diameter to luminally engage ablood vessel and formed of a material heatable from a remote, extra bodyheating assembly; and at least one said sensor is coupled in thermalexchange relationship with said stent.
 36. The implant system of claim35 in which: a first said sensor exhibits a first said predeterminedresonant center frequency at monitor temperatures below a first saidtemperature range, ΔT_(c1); and a second said sensor exhibits a secondsaid predetermined resonant center frequency different from said firstpredetermined resonant center frequency at monitor temperatures below asecond said temperature range, ΔT_(c2) above said first temperaturerange.
 37. The implant system of claim 35 in which: said at least onesensor component is fixed to said stent outer surface.
 38. The implantsystem of claim 37 further comprising: a non-magnetic flexible bandagalvanic with respect to said stent and surmounting said stent outersurface and said sensor, said band being generally diametricallyexpandable with said stent.
 39. The implant system of claim 37 furthercomprising: a thermally activatable release agent layer supported bysaid stent and effective to disperse when said stent is at a temperaturebelow or generally corresponding with said temperature range, ΔT_(c).40. A method for thermally treating a target tissue within the body of apatient, comprising the steps of: (a) determining temperature andtreatment interval therapy data for carrying out said treatment of saidtarget tissue; (b) providing one or more passive resonant implants, eachhaving an electromagnetic response of given intensity to an extra bodyapplied interrogational electromagnetic field at a predeterminedresonant center frequency only when said implant is at a monitortemperature or temperatures below a target temperature correspondingwith said therapy data; (c) providing a heating assembly controllable toderive an output effecting the generation of heat at said target tissuefrom an application component located externally of said body; (d)providing an interrogation assembly having an antenna assembly andcontrollable to derive and apply said extra body interrogationalelectromagnetic field and having a detector output in correspondencewith antenna assembly detections of said implant electromagneticresponse at said predetermined resonant center frequency; (e) locatingsaid one or more implants at an intra-body location effective forresponse to temperature at the location of said target tissue; (f)controlling said heating assembly to elevate the temperature of saidtarget tissue; (g) controlling said interrogation assembly to derive andapply said extra body interrogational electromagnetic field to saidlocated one or more implants for an interrogation interval deriving saiddetector output; and (h) controlling said heating assembly incorrespondence with said detector output.
 41. The method of claim 40 inwhich: said step (b) provides one or more of said passive resonantimplants as having a said electromagnetic response at a predeterminedresonant center frequency when said one or more implants are at a saidmonitor temperature or temperatures and exhibit a decrease in theintensity of said response at said predetermined resonant centerfrequency when approaching said target temperature corresponding withsaid temperature therapy data.
 42. The method of claim 40 in which: saidstep (b) provides one or more of said passive resonant implants ashaving a said electromagnetic response at a predetermined resonantcenter frequency when said one or more implants are at a said monitortemperature or temperatures and exhibit an absence of said response atsaid predetermined resonant center frequency when at said targettemperature.
 43. The method of claim 40 in which: said step (b) providesone or more of said passive resonant implants as an unteathered passiveresonant circuit with an inductance defining winding and core component,said core having a relative permeability characteristic exhibiting adrop in relative permeability toward a unity value at a Curietemperature corresponding with said target temperature, said circuitresonating at said predetermined resonant center frequency in responseto said applied interrogational electromagnetic field when at saidmonitor temperatures.
 44. The method of claim 40 in which: said step (b)provides one or more of said passive resonant implants as an unteatheredpassive resonant circuit with an inductor component and a capacitorcomponent, said capacitor component and/or said inductor componentexhibiting respective capacitance and/or inductance value or valuescorresponding with said temperature at the location of said targettissue.
 45. The method of claim 40 in which: said step (d) provides saidinterrogation assembly as deriving said detector output as a Fouriertransform corresponding with a said predetermined resonant centerfrequency.
 46. The method of claim 45 in which: said step (g) controlssaid interrogation assembly as deriving said detector output subsequentto said interrogation interval.
 47. The method of claim 46 in which:said step (d) provides said interrogation assembly as deriving saiddetector output as an average of a plurality of said antenna assemblydetections.
 48. The method of claim 40 in which: said step (a)determines said temperature therapy data as a temperature rangeextending from a threshold temperature to a limit temperature higherthan said threshold temperature; and said step (b) provides a first saidunteathered implant having a said electromagnetic response at a firstsaid resonant center frequency corresponding with monitor temperaturesbelow a said threshold temperature and provides a second saidunteathered implant having a said electromagnetic response at a secondsaid resonant center frequency, different than said first resonantfrequency, corresponding with monitor temperatures below said limittemperature.
 49. The method of claim 47 in which: said step (g) controlssaid heating assembly by effecting the generation of heat at said targettissue in the presence of a said detector output corresponding withtemperatures below said limit temperature.
 50. The method of claim 40 inwhich: said step (a) determines said temperature therapy data as atemperature range extending from a threshold temperature to a limittemperature higher than said threshold temperature; said step (b)provides a first said unteathered implant having a said electromagneticresponse at a said resonant center frequency corresponding withtemperatures below said threshold temperature, and provides a secondsaid unteathered implant as an auto-regulated heater component formed ofa ferromagnetic material within a non-magnetic material, saidferromagnetic material exhibiting a Curie temperature in correspondencewith said limit temperature precluding thermal response of saidnon-magnetic material to an applied alternating field; and said step (c)provides said heating assembly as controllable to apply alternatingcurrent field based heat-inducing energy to said target tissue and saidsecond implant; and said step (e) locates said first and second implantsat said intra-body location.
 51. The method of claim 50 in which: saidstep (g) controls said heating assembly to apply said alternating fieldbased current when said interrogation assembly is not being controlledto derive said detector output.
 52. The method of claim 40 in which:said step (b) provides one or more of said unteathered passive resonantimplants as having an electromagnetic response characteristic whereinsaid electromagnetic response at a predetermined resonant centerfrequency occurs when said one or more implants are at said monitortemperature or temperatures and said implant or implants exhibiting adecrease in the intensity of said response at said predeterminedresonant center frequency when approaching a said target temperaturecorresponding with said temperature therapy data; said step (c) providessaid heating assembly for the generation of said heat at said targettissue by the application of at least ultrasound frequency energy fromsaid application component; said step (g) controls said heating assemblyto apply said ultrasound energy in response to a said detector outputcorresponding with said electromagnetic response.
 53. The method ofclaim 52 in which: said step (b) provides a first said unteatheredimplant having a said electromagnetic response characteristic and asecond said unteathered implant as a heater component formed at least inpart with ultrasound absorptive material.
 54. The method of claim 40 inwhich: said step (a) determines said therapy data to effect induction oftherapeutic levels of heat shock protein from said target tissue volume.55. The method of claim 40 in which said step (a) determines saidtherapy data to effect hyperthermia therapy for the treatment of cancer.56. The method of claim 40 in which said step (a) determines saidtherapy data to effect thermal therapy for the repair of boney tissue.57. The method of claim 40 in which said step (a) determines saidtherapy data to effect induction of heat shock protein from a saidtissue carrying infectious disease.
 58. The method of claim 40 in which:said step (b) further comprises the step: (b1) providing one or moreheating components responsive to said heating assembly output to elevatein temperature; and said step (e) locates said one or more heatingcomponents at a said intra-body location effective for heating tissue.59. The method of claim 58 in which: said step (b1) provides a saidheating component as a stent having a generally cylindrically shapedoutward luminal engagement surface; said step (b) provides said implantas one or more temperature sensors coupled in thermal exchangerelationship with said stent; and said step (e) locates said stent andtemperature sensor within a blood vessel.
 60. The method of claim 59 inwhich: said step (b1) provides said heating component stent as furthercomprising a release agent material supported in thermal exchangerelationship therewith and responsive to effect its dispersion to limitrestenosis when said stent is at said determined temperature.
 61. Themethod of claim 59 in which: said step (b) provides a said temperaturesensor as being coupled with said stent outward luminal engagementsurface.
 62. The method of claim 59 in which: said steps (b) and (b1)provide said temperature sensor as being coupled with said stent with aflexible band surmounting said outward engagement surface and saidtemperature sensor.
 63. The method of claim 59 in which: said step (a)determines said therapy data to effect hyperthermia therapy for thetreatment of restenosis.
 64. The method of claim 59 in which: said step(c) provides said heating assembly output as an ultrasound output; andsaid step (b1) provides said stent as being formed of ultrasoundabsorbitive material.
 65. The method of claim 59 in which: said step (c)provides said heating assembly output as an alternating current basedfield; and said step (b1) provides said stent as being formed ofnon-magnetic material.
 66. An implant system for evaluating atemperature related physical parameter at a target tissue, comprising:an unteathered passive resonant circuit containing sensor with aninductor component and a capacitor component configured as a resonantcircuit, said capacitor component and/or said inductor componentexhibiting respective capacitance value or values and/or inductancevalue or values corresponding with a temperature of said target tissue,said circuit being responsive to a transient applied electromagneticfield to resonate at predetermined resonant frequencies correspondingwith said temperature or temperatures.
 67. The implant system of claim66 in which: said sensor has an externally disposed surface coated witha biocompatible conformal layer.
 68. The implant system-of claim 66further comprising: at least one tissue engaging implement fixed to andextending outwardly from said sensor and effective to engage tissue inadjacency therewith when implanted.
 69. The implant system of claim 66in which said implant system further comprises: a heater component inheat exchange relationship with said sensor and dimensioned with saidsensor to effect a minimally invasive implantation at said targettissue.
 70. The implant system of claim 66 further comprising: athermally activatable release agent coating extending over said sensorand effective to disperse said agent at the situs of said target tissue.71. The implant system of claim 69 in which said heater component isseparate from said sensor and is configured for implantation within saidtarget tissue in spaced relationship with said sensor.
 72. The implantsystem of claim 71 in which the surface of said heater componentsupports a thermally activatable release agent coating effective todisperse at the situs of said target tissue when said heater componentis at a temperature generally corresponding with said predeterminedtemperature.
 73. The implant system of claim 71 in which said heatercomponent is formed of a non-magnetic metal.
 74. The implant system ofclaim 71 in which said heater component is formed of ultrasoundabsorbative material.
 75. The implant system of claim 71 in which saidheater component further comprises at least one tissue engagingimplement fixed to and extending outwardly therefrom and effective toengage tissue in adjacency therewith when implanted.
 76. The implantsystem of claim 66 in which said sensor capacitor component exhibitscapacitance values varying with temperature to effect a correspondingvariation of said resonant frequencies.
 77. A temperature responsiveunteathered sensor implant for evaluating a temperature rise from amonitoring temperature or temperatures to a set point temperaturecomprising: a core component exhibiting a relative permeabilitycharacteristic elevating in value with a corresponding elevation inmonitoring temperatures and exhibiting a Curie temperature above saidmonitoring temperatures corresponding with said set point temperature;an inductive winding with turns wound about said core component todefine an inductive component; a capacitor coupled with said inductivewinding to define a resonant circuit electromagnetically excitable tohave a resonating output at a select resonant center frequency andexhibiting a decrease in the intensity of said resonating output at saidselect resonant center frequency when at temperatures approaching atsaid Curie temperature.
 78. The implant of claim 77 in which saidimplant further comprises: a non-magnetic heater component coupled inheat influencing relationship with said sensor implant at a locationsubstantially non-interfering with said resonating output.
 79. Theimplant of claim 77 in which: said defined resonant circuit exhibits anabsence of said resonating output at said select resonant centerfrequency when at said Curie temperature.
 80. The implant of claim 77 inwhich: said core component is formed of ferrite material.
 81. Theimplant of claim 77 in which: said select resonant center frequencycorresponds at least in part with the number of said turns of saidinductive winding.
 82. The implant of claim 77 in which: said selectresonant center frequency corresponds at least in part with the value ofcapacitance of said capacitor.
 83. The implant of claim 77 in which:said select center frequency corresponds with both the number of saidturns of said inductive winding and with the value of capacitance ofsaid capacitor.
 84. The implant of claim 77 in which: said corecomponent has an outer surface and extends along a component axisbetween oppositely disposed end surfaces; further comprising a firstelectrically insulative sleeve having a first sleeve outer surface andlocated over said core component outer surface and having oppositelydisposed first sleeve ends extending between or beyond said corecomponent end surfaces; and said inductive winding turns are wound oversaid sleeve outer surface.
 85. The implant of claim 84 in which: asecond electrically insulative sleeve having a second sleeve outersurface located over said inductive winding, having oppositely disposedsecond sleeve ends extending beyond said first sleeve ends.
 86. Theimplant of claim 85 in which: said capacitor is mounted within saidsecond sleeve between a said first sleeve end and an adjacent saidsecond sleeve end.
 87. The implant of claim 86 in which: said first andsecond sleeves are formed of polymeric material; and said second sleeveis potted with a biocompatible epoxy adhesive.
 88. The implant of claim86 in which said second sleeve, when potted, is coated with anelectrically insulative biocompatible conformal layer.
 89. The implantof claim 86 in which: said second sleeve is potted with saidbiocompatible epoxy adhesive wherein the outwardly disposed surface ofsaid epoxy adhesive is disposed inwardly from at least one of saidsecond sleeve ends to define an anchoring structure for engagement withanimal tissue.
 90. The implant of claim 86 further comprising: abiocompatible anchor structure configured for engagement with animaltissue mounted within and extending from at least one of said secondsleeve ends.
 91. The implant of claim 85 in which said implant furthercomprises: a non-magnetic heater component coupled in heat influencingrelationship with said sensor implant at a said second sleeve end. 92.The implant of claim 91 in which: said heater component is configured asan open ended sleeve coupled at the said second sleeve outer surface.93. The implant of claim 77 in which said implant further comprises: athermally activatable release agent supported by said implant andeffective to disperse when said implant is within tissue at or belowsaid transition temperature.
 94. A method for thermally treating targettissue within the body of a patient, comprising the steps of: (a)determining temperature and treatment interval therapy data for carryingout said treatment of said target tissue; (b) providing one or moreunteathered passive resonant sensor implants, each having anelectromagnetic response to an extra body applied interrogationalelectromagnetic field at a resonant center frequency when said sensorimplant is at monitor temperatures; (c) providing one or moreunteathered passive auto-regulating heaters having a thermal response toan extra body applied alternating current field to elevate intemperature to a predetermined temperature or temperatures, whereat saidheaters are thermally unresponsive to said applied alternating currentfield; (d) providing a heating assembly controllable to derive saidapplied alternating current field from an application component locatedexternally of said body effecting said thermal response; (e) providingan interrogation assembly having an antenna assembly and controllable toderive and apply said extra body interrogational electromagnetic fieldand having a detector output in correspondence with antenna assemblydetections of said sensor implant electromagnetic response at saidmonitor temperatures; (f) locating one or more said sensor implants atan intra-body location effective for response to temperature at thelocation of said target tissue; (g) locating one or more said heaters atan intra-body location effective for heating said target tissue; (h)controlling said heating assembly to elevate the temperature of said oneor more passive auto-regulating heaters; (i) controlling saidinterrogation assembly to derive and apply said extra bodyinterrogational electromagnetic field to said located one or more sensorimplants for an interrogational interval deriving said detector output;and (j) controlling said heating assembly in correspondence with saiddetector output.
 95. The method of claim 94 in which: said step (b)provides one or more of said unteathered passive resonant sensorimplants as having a said electromagnetic response at a predeterminedresonant center frequency when said one or more sensor implants are at asaid monitor temperature or temperatures and exhibit a decrease in theintensity of said response at said predetermined resonant centerfrequency when at temperatures approaching a target temperaturecondition corresponding with said temperature therapy data.
 96. Themethod of claim 94 in which: said step (b) provides one or more saidunteathered passive resonant sensor implants as having a saidelectromagnetic response at a predetermined resonant center frequencywhen said one or more sensor implants are at a said monitor temperatureor temperatures and exhibit an absence of said response at saidpredetermined resonant center frequency when at a target temperaturecondition corresponding with said temperature therapy data.
 97. Themethod of claim 94 in which: said step (b) provides one or more of saidpassive resonant sensor implants as a passive resonant circuit with aninductor component and a capacitor component, said capacitor componentand/or said inductor component exhibiting respective capacitance and/orinductance value or values corresponding with said temperature at thelocation of said target tissue.
 98. The method of claim 94 in which:said step (e) provides said interrogation assembly as deriving saiddetector output as a Fourier transform corresponding with saidpredetermined resonant center frequency.
 99. The method of claim 98 inwhich: said step (e) provides said interrogation assembly as derivingsaid detector output subsequent to said interrogation interval.
 100. Themethod of claim 99 in which: said step (e) provides said interrogationassembly as deriving said detector output as an average of a pluralityof said antenna assembly detections.
 101. The method of claim 94 inwhich: said step (a) determines said temperature therapy data as atemperature range extending from a threshold temperature to a limittemperature higher than said threshold temperature; said step (b)provides said one or more unteathered passive resonant sensors having asaid electromagnetic response at a said resonant center frequencycorresponding with monitor temperatures below a said thresholdtemperature; and said step (c) provides said one or more unteatheredpassive auto-regulating heaters to elevate in temperature to a saidpredetermined temperature corresponding with said limit temperature.102. The method on F6 in which: said step (b) provides said one or moreunteathered passive resonant sensors having a said electromagneticresponse at a said resonant center frequency corresponding with monitortemperatures below a said limit temperature.
 103. The method of claim 94in which: said step (a) determines said temperature therapy data as atemperature range extending from a threshold temperature to a limittemperature higher than said threshold temperature; said step (b)provides said one or more unteathered passive resonant sensors having asaid electromagnetic response at a said resonant center frequencycorresponding with monitor temperatures below a said limit temperature;and said step (c) provides said one or more unteathered passiveauto-regulating heaters to elevate in temperature to a saidpredetermined temperature corresponding with said threshold temperature.104. Stent apparatus for positioning within the body of a patient,comprising: a metal stent structure having a contact surface configuredfor abutting engagement with tissue of said patient and formed withmaterial responsive to energy non-invasively applied from an extra-bodysource to elevate in temperature; and a first passive resonant sensorattached to said stent structure having an electromagnetic response toan extra body applied interrogational electromagnetic field at monitortemperatures.
 105. The stent apparatus of claim 104 further comprising:a second passive resonant sensor attached to said stent structure havingan electromagnetic response to an extra-body applied interrogationalelectromagnetic field when at monitor temperatures.
 106. The stentapparatus of claim 104 in which: said first passive resonant sensor isresponsive to said interrogational electromagnetic field at a firstresonant center frequency when at said monitor temperatures and exhibitsa decrease in the intensity of said response at said first resonantcenter frequency when at temperatures approaching a hyperthermia basedfirst target temperature.
 107. The stent apparatus of claim 104 inwhich: said first passive resonant sensor is responsive to saidinterrogational electromagnetic field at a first resonant centerfrequency when at said monitor temperatures and exhibits an absence ofsaid response at said first resonant center frequency when at ahyperthermia based first target temperature.
 108. The stent apparatus ofclaim 104 in which: said second passive resonant sensor is responsive tosaid interrogational electromagnetic field at a second resonant centerfrequency when at said monitor temperatures and exhibits a decrease inthe intensity of said response at said second resonant center frequencywhen at temperatures approaching a hyperthermia based second targettemperature.
 109. The stent apparatus of claim 105 in which: said secondpassive resonant sensor is responsive to said interrogationalelectromagnetic field at a second resonant center frequency when at saidmonitor temperatures and exhibits an absence of said response at saidsecond resonant center frequency when at a hyperthermia based secondtarget temperature.
 110. The stent apparatus of claim 105 in which: saidfirst passive resonant sensor is attached to said metal stent structurecontact surface.
 111. The stent apparatus of claim 110 in which: saidsecond passive resonant sensor is attached to said stent structurecontact surface.
 112. The stent apparatus of claim 106 in which: saidsecond passive resonant sensor is responsive to said interrogationalelectromagnetic field at a second resonant center frequency when at saidmonitor temperatures and exhibits a decrease in the intensity of saidresponse at said second resonant center frequency when at a temperatureapproaching a hyperthermia based second target temperature.
 113. Thestent apparatus of claim 107 in which: said second passive resonantsensor is responsive to said interrogational electromagnetic field at asecond resonant center frequency when at said monitor temperatures andexhibits an absence of said response at said second resonant centerfrequency when at a hyperthermia based second target temperature. 114.The stent apparatus of claim 113 in which: said first passive resonantsensor is configured to exhibit said decrease in the intensity of saidresponse when at temperatures approaching a lower threshold first saidtarget temperature and said second passive resonant sensor is configuredto exhibit said decrease in the intensity of said response when attemperatures approaching an upper limit second said target temperature.115. The stent apparatus of claim 113 in which: said first passiveresonant sensor is configured to exhibit said absence of said responseat said first resonant center frequency when at a lower threshold firstsaid target temperature; and said second passive resonant sensor isconfigured to exhibit said absence of said response at said secondresonant center frequency when at an upper limit second said targettemperature.
 116. The stent apparatus of claim 110 further comprising: aflexible securement band agalvanic with respect to said metal stentstructure and tensionally surmounting said metal stent structure andsaid first sensor.
 117. The stent apparatus of claim 111 furthercomprising: a flexible securement band agalvanic with respect to saidmetal stent structure and tensionally surmounting said metal stentstructure and said second sensor.
 118. The stent apparatus of claim 104further comprising: a thermally activatable release agent coatingextending within said metal stent structure, effective to limitrestenosis when dispersed at said hyperthermia based temperature level.119. A system for evaluating a temperature related physical parameter ata target region of a patient, comprising: one or more teatherlesspassive resonant implants located internally within said patient inthermally responsive relationship with said target region, each saidimplant having a unique resonant electromagnetic response within afrequency bandwidth of responses in reaction to an extra body appliedelectromagnetic field when said implant is at a monitor temperature ortemperatures; an excitation assembly comprising an excitation antennapositionable adjacent said patient at a location effective to derivesaid unique electromagnetic response, a high voltage power supply havinga high voltage output, when enabled, a resonant excitation circuitcoupled with said excitation antenna and responsive to an excite signalto effect generation of said applied electromagnetic field for anexcitation interval; a detector assembly comprising a sense antennapositionable adjacent said patient at a location effective, when saiddetector assembly is enabled, to detect said unique electromagneticresponse as a sense antenna output, a bandpass filter network coupled tofilter said sense antenna output in correspondence with said frequencybandwidth of responses, and an amplifier network configured to amplifysaid filtered sense antenna output to provide an amplified output; acontrol circuit responsive to derive said excite signal for saidexcitation interval, subsequently responsive to enable said detectorassembly to permit derivation of said amplified output; a dataacquisition and control network responsive to sample and digitize saidamplified output to provide digitized waveform data, to derive frequencyintensity signals therefrom about the center frequencies of each saidunique resonant electromagnetic response when a said implant is at asaid monitor temperature or temperatures, responsive to said frequencyintensity signals and implant identification data representing acorresponding unique resonant electromagnetic response to derive implantstatus data; and a readout assembly responsive to said implant statusdata to provide a discernable readout corresponding therewith.
 120. Thesystem of claim 119 in which: said excitation assembly further comprisesa voltage monitor network responsive to said high voltage output and avoltage threshold reference to derive a voltage monitor output conditionwhen said high voltage output is at an operating level; and said controlcircuit is responsive to a start input and said voltage monitor outputcondition to derive said excite signal.
 121. The system of claim 119 inwhich: said control circuit is responsive to enable said detectorassembly following a delay interval occurring subsequent to saidexcitation interval.
 122. The system of claim 121 in which: saiddetector assembly further comprises paired solid state enablementswitches coupled intermediate said sense antenna output and saidbandpass filter network having a normally de-coupling condition andgatable into a conducting condition; and said control circuit isresponsive to enable said detector assembly by effecting the gating ofsaid enablement switches into said conducting condition.
 123. The systemof claim 119 in which: said detector assembly bandpass filter exhibits abandpass from about 100 kilohertz to about 2 megahertz.
 124. The systemof claim 119 in which: said data acquisition and control network isresponsive to average a plurality of said digitized waveforms to deriveaveraged digitized waveforms, and is responsive to derive Fouriertransforms of said averaged digitized waveforms to derive said frequencyintensity signals;
 125. The system of claim 119 in which: said readoutassembly provides said discernable readout as a visibly perceptibleoutput corresponding with each said one or more implant.
 126. The systemof claim 125 in which: said one or more teatherless passive resonantimplants exhibits a dimunition of the intensity of said unique resonantelectromagnetic response when at temperatures approaching a targettemperature above said monitor temperature or temperatures.
 127. Thesystem of claim 125 in which: said one or more teatherless passiveresonant implants exhibits an absence of said unique resonantelectromagnetic response when at a target temperature above said monitortemperature or temperatures.
 128. The system of claim 119 in which: saiddetector sense antenna is flexible and is positioned upon said patientin an orientation conforming with the body shape of said patient. 129.The system of claim 119 in which: said control circuit is configured toenable said high voltage power supply in response to said excite signal130. A system for thermally treating a target tissue within the body ofa patient, comprising: one or more teatherless passive resonant sensorslocated internally within said patient in thermally responsiverelationship with said target tissue, each said sensor having a uniqueelectromagnetic response within a frequency bandwidth of responses inreaction to an extra body applied electromagnetic field when a saidsensor is at a monitor temperature or temperatures, and exhibiting adecrease in the intensity of said unique resonant electromagneticresponse when approaching a target temperature above said monitortemperature or temperatures; a heating assembly actuable to applyheat-inducing energy to said target tissue to an extent effective toelevate the temperature toward said target temperature and de-actuableto terminate said application of heat-inducting energy; an excitationassembly comprising an excitation antenna positionable adjacent saidpatient at a location effective to derive said unique electromagneticresponse, a high voltage power supply having a high voltage output, whenenabled, a resonant excitation circuit coupled with said excitationantenna and responsive to an excite signal to effect generation of saidapplied electromagnetic field for an excitation interval; a detectorassembly comprising a sense antenna positionable adjacent said patientat a location effective, when said detector assembly is enabled, todetect said unique electromagnetic response as a sense antenna output, abandpass filter network coupled to filter said sense antenna output incorrespondence with said frequency bandwidth of responses, and anamplifier network responsive to said bandpass output to provide anamplified output; a monitor control circuit responsive to derive saidexcite signal for said excitation interval, subsequently responsive toenable said detector assembly to permit derivation of said amplifiedoutput; a data acquisition network responsive to sample and digitizesaid amplified output to provide digitized waveform data and to derivefrequency intensity data therefrom about the center frequencies of eachsaid unique resonant electromagnetic response when said implant is at asaid monitor temperature or temperatures, responsive to said frequencyintensity data or said absence thereof and implant identification datarepresenting a corresponding unique resonant electromagnetic response toderive sensor status data; and a controller, operator actuable to derivesaid monitor control circuit start input and having a readout assemblyresponsive to said sensor status data to provide a visibly perceptiblecorresponding therewith.
 131. The system of claim 130 in which: said oneor more teatherless passive resonant sensors each has a said uniqueelectromagnetic response in reaction to an extra-body appliedelectromagnetic field when a said sensor is at a monitor temperature ortemperatures, and exhibits an absence of said unique electromagneticresponse when at said target temperature; and said data acquisitionnetwork is responsive to said frequency intensity data or the absencethereof and implant identification data representing a correspondingunique resonant electromagnetic response to derive said sensor statusdata.
 132. The system of claim 130 in which: said controller readoutcomprises one or more arrays of light output components, each said lightoutput component having an illumination state corresponding with theoperating condition of a unique said sensor.
 133. The system of claim130 in which: said heating assembly is actuable to apply alternatingcurrent inductive field based thermal energy to said target tissue; andsaid controller is responsive to a said data acquisition network sensorstatus data corresponding with a said sensor at a said monitortemperature to provide said start input for an interrogation intervaland is responsive at the termination of said interrogation interval toterminate said start input and actuate said heating assembly for aheating interval.
 134. The system of claim 133 in which: a said sensoris coupled with a stent positioned inter-luminally with a blood vessel.135. An implant for employment in developing a thermotherapy set pointtemperature at a target tissue when disposed in thermal exchangetherewith, comprising: an unteathered passive resonant circuit with aninductance defining core component formulated with oxides of Fe, Mn andZn to exhibit a Curie point temperature corresponding with said setpoint temperature, said circuit being responsive to a transient appliedelectromagnetic field to resonate at a predetermined resonant centerfrequency at temperatures below said set point temperature.
 136. Theimplant of claim 135 in which: said core component further comprises anoxide of CA in an amount effective to provide a core componentresistivity greater than about 100 ohm-cm.
 137. The system of claim 135in which: said core component further comprises an oxide of CA in anamount effective to provide a core component resistivity greater thanabout 500 ohm-cm.
 138. The system of claim 135 in which: said corecomponent further comprises an oxide of CA in an amount effective toprovide a core component resistivity greater than about 700 ohm-cm.